<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:f52076c7-5aeb-48b3-b15e-b7164d2e58bb,g:2dce0b88-f1d3-43c4-84fa-04b35e9df954-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.datadoghq.com/role/CoverPage" xlink:type="simple" xlink:href="ddog-20220331.xsd#CoverPage"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/CoverPage" xlink:type="extended" id="i9de0eb562f134a2a833bfcc2488ee4bb_CoverPage">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_2b9403e9-28e1-45b2-816d-9d4ec5aa31cd" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_DocumentType_2b9403e9-28e1-45b2-816d-9d4ec5aa31cd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_111c79c6-5683-4016-8e18-612a2a5fe507" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_DocumentQuarterlyReport_111c79c6-5683-4016-8e18-612a2a5fe507" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_66c48745-fde9-444f-823a-1b13a8e999e5" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_DocumentPeriodEndDate_66c48745-fde9-444f-823a-1b13a8e999e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_3888c545-98cf-4515-ac0b-099bfbc09ceb" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_DocumentTransitionReport_3888c545-98cf-4515-ac0b-099bfbc09ceb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_d0d8c284-8dbc-4449-a4c6-a8629d37ca22" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityFileNumber_d0d8c284-8dbc-4449-a4c6-a8629d37ca22" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_62f0f210-e353-445d-80ad-0ea110d3dbc8" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityRegistrantName_62f0f210-e353-445d-80ad-0ea110d3dbc8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_7dbfab9b-7c62-4943-8d29-93b41c8127e0" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityIncorporationStateCountryCode_7dbfab9b-7c62-4943-8d29-93b41c8127e0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_b41b7251-ab99-43ea-82c0-f02f65a19045" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityTaxIdentificationNumber_b41b7251-ab99-43ea-82c0-f02f65a19045" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_6a180670-5112-4b69-83c2-d33411499489" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityAddressAddressLine1_6a180670-5112-4b69-83c2-d33411499489" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_45a06a4f-5c36-4e7f-8e72-378db1fb09a1" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityAddressAddressLine2_45a06a4f-5c36-4e7f-8e72-378db1fb09a1" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_e436c242-4ce0-4b29-af50-7f16bef6024a" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityAddressCityOrTown_e436c242-4ce0-4b29-af50-7f16bef6024a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_f01d7167-7040-46ac-89cb-4ee7a5b655f9" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityAddressStateOrProvince_f01d7167-7040-46ac-89cb-4ee7a5b655f9" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_af7ad1e1-0f65-49a1-910f-dab2e07141d7" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityAddressPostalZipCode_af7ad1e1-0f65-49a1-910f-dab2e07141d7" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_dda8b569-ebe5-4a8d-9330-2b2e43f54bfa" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_CityAreaCode_dda8b569-ebe5-4a8d-9330-2b2e43f54bfa" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_5358ef02-626b-4767-ab7e-28f6b31f3fea" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_LocalPhoneNumber_5358ef02-626b-4767-ab7e-28f6b31f3fea" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_e99acb4b-3b1a-4c71-b569-570ae315d3c4" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_Security12bTitle_e99acb4b-3b1a-4c71-b569-570ae315d3c4" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_434daa91-5a7e-4abe-bd10-3d527f12c245" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_TradingSymbol_434daa91-5a7e-4abe-bd10-3d527f12c245" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_8ea2936f-422a-495a-a76e-6509ec6b2e24" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_SecurityExchangeName_8ea2936f-422a-495a-a76e-6509ec6b2e24" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_c2da3194-12d7-4bc9-833f-0a09afeff948" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityCurrentReportingStatus_c2da3194-12d7-4bc9-833f-0a09afeff948" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_fa9cf8ab-965f-40e8-95f0-2b8d88b5e967" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityInteractiveDataCurrent_fa9cf8ab-965f-40e8-95f0-2b8d88b5e967" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_0c403450-ad7b-4d1d-9795-2ca7e8cd3ef2" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityFilerCategory_0c403450-ad7b-4d1d-9795-2ca7e8cd3ef2" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_2eaf0bf1-3963-46ab-9571-37ba224eb89d" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntitySmallBusiness_2eaf0bf1-3963-46ab-9571-37ba224eb89d" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_514589c1-4571-4041-b334-7d8c3134c95e" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityEmergingGrowthCompany_514589c1-4571-4041-b334-7d8c3134c95e" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_e3b1504e-5b82-4a53-b49d-f484ba014f5a" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityShellCompany_e3b1504e-5b82-4a53-b49d-f484ba014f5a" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_0cf137b4-46ee-4fb4-8b4f-61dbb2f80c7e" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_0cf137b4-46ee-4fb4-8b4f-61dbb2f80c7e" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_b99d9e35-880b-4aa6-a97b-4f5bc083264a" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_AmendmentFlag_b99d9e35-880b-4aa6-a97b-4f5bc083264a" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_5d31f3b2-8d47-401b-a186-079b25b7e871" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_DocumentFiscalYearFocus_5d31f3b2-8d47-401b-a186-079b25b7e871" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_6d7ec191-261b-42a6-b587-3c4aa0ce5c68" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_DocumentFiscalPeriodFocus_6d7ec191-261b-42a6-b587-3c4aa0ce5c68" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_3fe98ce4-ca7d-4c11-a672-5b59ac4cc302" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_EntityCentralIndexKey_3fe98ce4-ca7d-4c11-a672-5b59ac4cc302" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_76c5330d-fd8e-4f57-ad16-dccd5bda2360" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_CurrentFiscalYearEndDate_76c5330d-fd8e-4f57-ad16-dccd5bda2360" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_2b8abbe6-ca19-412a-a13d-725a914e8f67" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_ab21985c-a800-4960-b1c8-29ee447be5a3" xlink:to="loc_dei_DocumentInformationTable_2b8abbe6-ca19-412a-a13d-725a914e8f67" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_3443e2f8-5e5f-4ee9-92c2-f2a8f2b96c7c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_2b8abbe6-ca19-412a-a13d-725a914e8f67" xlink:to="loc_us-gaap_StatementClassOfStockAxis_3443e2f8-5e5f-4ee9-92c2-f2a8f2b96c7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_3443e2f8-5e5f-4ee9-92c2-f2a8f2b96c7c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_3443e2f8-5e5f-4ee9-92c2-f2a8f2b96c7c" xlink:to="loc_us-gaap_ClassOfStockDomain_3443e2f8-5e5f-4ee9-92c2-f2a8f2b96c7c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_aa99c1e2-f378-4304-b95c-09b2c39660d3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_3443e2f8-5e5f-4ee9-92c2-f2a8f2b96c7c" xlink:to="loc_us-gaap_ClassOfStockDomain_aa99c1e2-f378-4304-b95c-09b2c39660d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_27e1f11c-3300-45ca-af99-797017a929e1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_aa99c1e2-f378-4304-b95c-09b2c39660d3" xlink:to="loc_us-gaap_CommonClassAMember_27e1f11c-3300-45ca-af99-797017a929e1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_12939db7-de58-4bc5-95b0-cc982e7b147a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_aa99c1e2-f378-4304-b95c-09b2c39660d3" xlink:to="loc_us-gaap_CommonClassBMember_12939db7-de58-4bc5-95b0-cc982e7b147a" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="ddog-20220331.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETS"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="extended" id="i9af0f98761924aa9813b9d6892391637_CONDENSEDCONSOLIDATEDBALANCESHEETS">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_24fd013d-1933-4141-b60f-38ded6b1f7d4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_c28e964f-2e97-41c9-a9f5-f47a3672050a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_24fd013d-1933-4141-b60f-38ded6b1f7d4" xlink:to="loc_us-gaap_AssetsAbstract_c28e964f-2e97-41c9-a9f5-f47a3672050a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_f031b33c-ed40-4c29-bd67-a3adafe18552" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_c28e964f-2e97-41c9-a9f5-f47a3672050a" xlink:to="loc_us-gaap_AssetsCurrentAbstract_f031b33c-ed40-4c29-bd67-a3adafe18552" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_d3c241f5-a924-46cd-a808-b11f5756c0f0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_f031b33c-ed40-4c29-bd67-a3adafe18552" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_d3c241f5-a924-46cd-a808-b11f5756c0f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_b0b2ef69-bf90-401e-bc0c-ec026d8b4ba2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_f031b33c-ed40-4c29-bd67-a3adafe18552" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_b0b2ef69-bf90-401e-bc0c-ec026d8b4ba2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_84e7e1cf-f815-4073-b62e-344f41e673a5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_f031b33c-ed40-4c29-bd67-a3adafe18552" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_84e7e1cf-f815-4073-b62e-344f41e673a5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCostsCurrent_0061a0e5-d865-42c2-aa20-340169296077" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCostsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_f031b33c-ed40-4c29-bd67-a3adafe18552" xlink:to="loc_us-gaap_DeferredCostsCurrent_0061a0e5-d865-42c2-aa20-340169296077" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_237ef364-17b0-4bc5-9e06-b48789bc0878" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_f031b33c-ed40-4c29-bd67-a3adafe18552" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_237ef364-17b0-4bc5-9e06-b48789bc0878" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_356bdc6f-2bfd-4f57-a6e1-86d0f908daff" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_f031b33c-ed40-4c29-bd67-a3adafe18552" xlink:to="loc_us-gaap_AssetsCurrent_356bdc6f-2bfd-4f57-a6e1-86d0f908daff" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_9701078d-505a-4367-b6f7-5a3b8e2b2ddb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_c28e964f-2e97-41c9-a9f5-f47a3672050a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_9701078d-505a-4367-b6f7-5a3b8e2b2ddb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_34b522b9-3262-4282-84f7-2e6436bef13b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_c28e964f-2e97-41c9-a9f5-f47a3672050a" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_34b522b9-3262-4282-84f7-2e6436bef13b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_d4622a13-0d28-4401-a56a-406bea6079a3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_c28e964f-2e97-41c9-a9f5-f47a3672050a" xlink:to="loc_us-gaap_Goodwill_d4622a13-0d28-4401-a56a-406bea6079a3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_f01d6873-7d18-427e-b894-6bd612f9cdc9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_c28e964f-2e97-41c9-a9f5-f47a3672050a" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_f01d6873-7d18-427e-b894-6bd612f9cdc9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCosts_cac053ce-27f4-41f8-844c-0ef7d5b9ace3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_c28e964f-2e97-41c9-a9f5-f47a3672050a" xlink:to="loc_us-gaap_DeferredCosts_cac053ce-27f4-41f8-844c-0ef7d5b9ace3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashNoncurrent_cb7c8047-9cf1-4ac7-bd3d-feb00a2aa421" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedCashNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_c28e964f-2e97-41c9-a9f5-f47a3672050a" xlink:to="loc_us-gaap_RestrictedCashNoncurrent_cb7c8047-9cf1-4ac7-bd3d-feb00a2aa421" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_7442e93a-09a1-4ea2-b7bb-9f1eea97193a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_c28e964f-2e97-41c9-a9f5-f47a3672050a" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_7442e93a-09a1-4ea2-b7bb-9f1eea97193a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_4ae13db8-dd20-4f0b-ace6-a5ff6e325b3d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_c28e964f-2e97-41c9-a9f5-f47a3672050a" xlink:to="loc_us-gaap_Assets_4ae13db8-dd20-4f0b-ace6-a5ff6e325b3d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a92802ea-48f1-466a-ba44-13f7163bcb15" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_24fd013d-1933-4141-b60f-38ded6b1f7d4" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a92802ea-48f1-466a-ba44-13f7163bcb15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_448f4c8c-806e-4ac1-8eff-6eb119eae100" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a92802ea-48f1-466a-ba44-13f7163bcb15" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_448f4c8c-806e-4ac1-8eff-6eb119eae100" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_40d40e87-9cb1-4dc7-b943-7f61010ebedc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_448f4c8c-806e-4ac1-8eff-6eb119eae100" xlink:to="loc_us-gaap_AccountsPayableCurrent_40d40e87-9cb1-4dc7-b943-7f61010ebedc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilities_b7c370b6-9e0b-4e7f-9121-f36831387543" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccruedLiabilitiesAndOtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_448f4c8c-806e-4ac1-8eff-6eb119eae100" xlink:to="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilities_b7c370b6-9e0b-4e7f-9121-f36831387543" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_121f6d42-e5b9-40d6-b83c-d2646ebca03f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_448f4c8c-806e-4ac1-8eff-6eb119eae100" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_121f6d42-e5b9-40d6-b83c-d2646ebca03f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_573cc219-9692-4ac5-b169-50cb73b525b3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_448f4c8c-806e-4ac1-8eff-6eb119eae100" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_573cc219-9692-4ac5-b169-50cb73b525b3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_a6aa3b80-ca66-42b9-b703-6b31179fd939" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_448f4c8c-806e-4ac1-8eff-6eb119eae100" xlink:to="loc_us-gaap_LiabilitiesCurrent_a6aa3b80-ca66-42b9-b703-6b31179fd939" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_1d982399-02cd-474b-a106-a49fa9114e62" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a92802ea-48f1-466a-ba44-13f7163bcb15" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_1d982399-02cd-474b-a106-a49fa9114e62" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleLongTermNotesPayable_7f65f359-19b1-4892-8066-c27b4ba07fa6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleLongTermNotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a92802ea-48f1-466a-ba44-13f7163bcb15" xlink:to="loc_us-gaap_ConvertibleLongTermNotesPayable_7f65f359-19b1-4892-8066-c27b4ba07fa6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_c6e48245-84e9-4131-b4ab-bf22318a2c52" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a92802ea-48f1-466a-ba44-13f7163bcb15" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_c6e48245-84e9-4131-b4ab-bf22318a2c52" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_8a49ea4a-dc35-4d6a-a7c8-af316987a0df" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a92802ea-48f1-466a-ba44-13f7163bcb15" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_8a49ea4a-dc35-4d6a-a7c8-af316987a0df" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_b1518e52-86cf-4b37-9920-95e69ff3f621" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a92802ea-48f1-466a-ba44-13f7163bcb15" xlink:to="loc_us-gaap_Liabilities_b1518e52-86cf-4b37-9920-95e69ff3f621" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_844a6281-2e3b-4734-bfdf-4064c81e0106" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a92802ea-48f1-466a-ba44-13f7163bcb15" xlink:to="loc_us-gaap_CommitmentsAndContingencies_844a6281-2e3b-4734-bfdf-4064c81e0106" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityAbstract_1d5a4ce2-83c2-4cb7-a6ad-1db5351df3fa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a92802ea-48f1-466a-ba44-13f7163bcb15" xlink:to="loc_us-gaap_StockholdersEquityAbstract_1d5a4ce2-83c2-4cb7-a6ad-1db5351df3fa" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_a6da2b9a-c991-401c-a9a3-93ea52a39c73" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_1d5a4ce2-83c2-4cb7-a6ad-1db5351df3fa" xlink:to="loc_us-gaap_CommonStockValue_a6da2b9a-c991-401c-a9a3-93ea52a39c73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_ce3fdc2e-b3bd-4be3-9193-ee1f30984413" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_1d5a4ce2-83c2-4cb7-a6ad-1db5351df3fa" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_ce3fdc2e-b3bd-4be3-9193-ee1f30984413" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_34bfb49f-766b-4750-8dd2-104284011ab2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_1d5a4ce2-83c2-4cb7-a6ad-1db5351df3fa" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_34bfb49f-766b-4750-8dd2-104284011ab2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_8a4cfa52-db48-48fb-b3c5-0867042a3782" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_1d5a4ce2-83c2-4cb7-a6ad-1db5351df3fa" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_8a4cfa52-db48-48fb-b3c5-0867042a3782" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_a71f56b3-89ea-4241-b10f-6034e397a6b9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_1d5a4ce2-83c2-4cb7-a6ad-1db5351df3fa" xlink:to="loc_us-gaap_StockholdersEquity_a71f56b3-89ea-4241-b10f-6034e397a6b9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_f6bf3d9a-7caf-49f1-aa6c-7989d9ca706b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a92802ea-48f1-466a-ba44-13f7163bcb15" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_f6bf3d9a-7caf-49f1-aa6c-7989d9ca706b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_74e089b0-be5b-4d36-8d8a-ed232a617958" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_24fd013d-1933-4141-b60f-38ded6b1f7d4" xlink:to="loc_us-gaap_StatementTable_74e089b0-be5b-4d36-8d8a-ed232a617958" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_d03f23a3-c5b5-489c-b3e5-76344ccedec3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_74e089b0-be5b-4d36-8d8a-ed232a617958" xlink:to="loc_us-gaap_StatementClassOfStockAxis_d03f23a3-c5b5-489c-b3e5-76344ccedec3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_d03f23a3-c5b5-489c-b3e5-76344ccedec3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_d03f23a3-c5b5-489c-b3e5-76344ccedec3" xlink:to="loc_us-gaap_ClassOfStockDomain_d03f23a3-c5b5-489c-b3e5-76344ccedec3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_a91c8bca-1231-4593-83ad-032598c310d1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_d03f23a3-c5b5-489c-b3e5-76344ccedec3" xlink:to="loc_us-gaap_ClassOfStockDomain_a91c8bca-1231-4593-83ad-032598c310d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_35b21594-23b5-43c2-9d40-1917888aef8d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_a91c8bca-1231-4593-83ad-032598c310d1" xlink:to="loc_us-gaap_CommonClassAMember_35b21594-23b5-43c2-9d40-1917888aef8d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_1578da00-8f4b-4e04-b627-221c2ab80e5b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_a91c8bca-1231-4593-83ad-032598c310d1" xlink:to="loc_us-gaap_CommonClassBMember_1578da00-8f4b-4e04-b627-221c2ab80e5b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="simple" xlink:href="ddog-20220331.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="extended" id="i6709b388724a4680a2dd434f31d181e3_CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_5c895095-8a89-4fc9-b56d-724b32bd4604" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_8073c8c6-e23d-40b5-910c-fa8fbda6a065" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5c895095-8a89-4fc9-b56d-724b32bd4604" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_8073c8c6-e23d-40b5-910c-fa8fbda6a065" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_713142e1-8ec1-427a-bc62-c3f76c6913ed" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5c895095-8a89-4fc9-b56d-724b32bd4604" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_713142e1-8ec1-427a-bc62-c3f76c6913ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_138ce65f-9725-4369-a199-d06e9337d2cb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5c895095-8a89-4fc9-b56d-724b32bd4604" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_138ce65f-9725-4369-a199-d06e9337d2cb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_7732121a-1a34-4b8b-80db-a69b984046cd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5c895095-8a89-4fc9-b56d-724b32bd4604" xlink:to="loc_us-gaap_CommonStockSharesIssued_7732121a-1a34-4b8b-80db-a69b984046cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_18ff7d5a-148d-4f21-baa6-31827b6e471d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5c895095-8a89-4fc9-b56d-724b32bd4604" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_18ff7d5a-148d-4f21-baa6-31827b6e471d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_232ca242-a403-4d92-8138-39b25150e0fc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_5c895095-8a89-4fc9-b56d-724b32bd4604" xlink:to="loc_us-gaap_StatementTable_232ca242-a403-4d92-8138-39b25150e0fc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_52e66c54-e5ec-4106-a118-aaa52bbec36f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_232ca242-a403-4d92-8138-39b25150e0fc" xlink:to="loc_us-gaap_StatementClassOfStockAxis_52e66c54-e5ec-4106-a118-aaa52bbec36f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_52e66c54-e5ec-4106-a118-aaa52bbec36f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_52e66c54-e5ec-4106-a118-aaa52bbec36f" xlink:to="loc_us-gaap_ClassOfStockDomain_52e66c54-e5ec-4106-a118-aaa52bbec36f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_cdf12ff7-5cae-4a85-9598-4bcafaeff636" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_52e66c54-e5ec-4106-a118-aaa52bbec36f" xlink:to="loc_us-gaap_ClassOfStockDomain_cdf12ff7-5cae-4a85-9598-4bcafaeff636" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_d179be68-9e24-4f58-8b22-82c06c6a6d37" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_cdf12ff7-5cae-4a85-9598-4bcafaeff636" xlink:to="loc_us-gaap_CommonClassAMember_d179be68-9e24-4f58-8b22-82c06c6a6d37" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_0d5d1b42-18e5-4c8c-966c-c127fd5856fe" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_cdf12ff7-5cae-4a85-9598-4bcafaeff636" xlink:to="loc_us-gaap_CommonClassBMember_0d5d1b42-18e5-4c8c-966c-c127fd5856fe" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="simple" xlink:href="ddog-20220331.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="extended" id="i9abe9d875e7444a7b116b79ea59cd9e5_CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_40332b28-ca1f-42af-8d4d-b06f1c9b5dd5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_40332b28-ca1f-42af-8d4d-b06f1c9b5dd5" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_cf1e1107-4dff-4637-aa5f-8068fef5d6b0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:to="loc_us-gaap_SharesOutstanding_cf1e1107-4dff-4637-aa5f-8068fef5d6b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_94e1c996-71dc-4e99-8c0e-d570ca72d150" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:to="loc_us-gaap_StockholdersEquity_94e1c996-71dc-4e99-8c0e-d570ca72d150" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_fdb7e6bb-9845-471c-ab49-0fccb05d2efa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_fdb7e6bb-9845-471c-ab49-0fccb05d2efa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_d080e76c-fe7b-4189-b2c4-6226398096a2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_d080e76c-fe7b-4189-b2c4-6226398096a2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_StockIssuedDuringPeriodValueVestingOfEarlyExercisedStockOptions_5cc7e433-6338-4276-a581-a02cc93f0bb7" xlink:href="ddog-20220331.xsd#ddog_StockIssuedDuringPeriodValueVestingOfEarlyExercisedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:to="loc_ddog_StockIssuedDuringPeriodValueVestingOfEarlyExercisedStockOptions_5cc7e433-6338-4276-a581-a02cc93f0bb7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_StockIssuedDuringPeriodSharesVestingOfRestrictedStockUnits_95209cd6-6a0c-432d-b78e-b76e4589e881" xlink:href="ddog-20220331.xsd#ddog_StockIssuedDuringPeriodSharesVestingOfRestrictedStockUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:to="loc_ddog_StockIssuedDuringPeriodSharesVestingOfRestrictedStockUnits_95209cd6-6a0c-432d-b78e-b76e4589e881" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_40cb7c4f-88eb-4c95-bd8e-cfb8bad363d6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_40cb7c4f-88eb-4c95-bd8e-cfb8bad363d6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_c6483e14-c9cd-46d5-bbeb-71d1d8475c17" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_c6483e14-c9cd-46d5-bbeb-71d1d8475c17" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_9b02c3f0-be6e-4103-8788-b274441ea423" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_9b02c3f0-be6e-4103-8788-b274441ea423" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_192b9953-54eb-4b9a-8ca8-11bac31bdf54" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_192b9953-54eb-4b9a-8ca8-11bac31bdf54" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_88338482-7efb-4a7c-81cc-e0d235673d89" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:to="loc_us-gaap_NetIncomeLoss_88338482-7efb-4a7c-81cc-e0d235673d89" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountingStandardsUpdateExtensibleList_2e2a4117-89c0-4022-a1e5-063c05fb79ae" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountingStandardsUpdateExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_7238392f-6bc4-41e0-8472-409b45c73c62" xlink:to="loc_us-gaap_AccountingStandardsUpdateExtensibleList_2e2a4117-89c0-4022-a1e5-063c05fb79ae" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_a7707c1d-05ae-4007-813f-0dd813efaac2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_1df9bdaf-d4d8-4fb4-a4ed-398d764874cd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_c08e8380-14c0-47f9-9026-ce952185d7aa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_40332b28-ca1f-42af-8d4d-b06f1c9b5dd5" xlink:to="loc_us-gaap_StatementTable_c08e8380-14c0-47f9-9026-ce952185d7aa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_7356285a-79a5-41c2-82e7-72f7db13c606" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_c08e8380-14c0-47f9-9026-ce952185d7aa" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_7356285a-79a5-41c2-82e7-72f7db13c606" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_7356285a-79a5-41c2-82e7-72f7db13c606_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_7356285a-79a5-41c2-82e7-72f7db13c606" xlink:to="loc_us-gaap_EquityComponentDomain_7356285a-79a5-41c2-82e7-72f7db13c606_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_b5070f7b-95b8-4eec-8933-2e557d25658e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_7356285a-79a5-41c2-82e7-72f7db13c606" xlink:to="loc_us-gaap_EquityComponentDomain_b5070f7b-95b8-4eec-8933-2e557d25658e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_f0d740ee-a649-4aab-9c34-71ebfab32206" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_b5070f7b-95b8-4eec-8933-2e557d25658e" xlink:to="loc_us-gaap_CommonStockMember_f0d740ee-a649-4aab-9c34-71ebfab32206" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_756b5893-488c-4adf-90a7-1b86dd07c513" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_b5070f7b-95b8-4eec-8933-2e557d25658e" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_756b5893-488c-4adf-90a7-1b86dd07c513" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b30f1cf6-495c-4d10-b9d7-a2f952470cfc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_b5070f7b-95b8-4eec-8933-2e557d25658e" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b30f1cf6-495c-4d10-b9d7-a2f952470cfc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_e91f4a50-b65f-433f-b67d-6450edf736fc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_b5070f7b-95b8-4eec-8933-2e557d25658e" xlink:to="loc_us-gaap_RetainedEarningsMember_e91f4a50-b65f-433f-b67d-6450edf736fc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_3ead7762-1b50-469c-803d-2ce72bbaf090" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_c08e8380-14c0-47f9-9026-ce952185d7aa" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_3ead7762-1b50-469c-803d-2ce72bbaf090" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_3ead7762-1b50-469c-803d-2ce72bbaf090_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_3ead7762-1b50-469c-803d-2ce72bbaf090" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_3ead7762-1b50-469c-803d-2ce72bbaf090_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_606b6a04-d987-404d-8e98-47d76fd135c4" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_3ead7762-1b50-469c-803d-2ce72bbaf090" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_606b6a04-d987-404d-8e98-47d76fd135c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_0d9682a2-a72e-45bc-988b-cfd0587e3039" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_606b6a04-d987-404d-8e98-47d76fd135c4" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_0d9682a2-a72e-45bc-988b-cfd0587e3039" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember_fd7fd04a-d58c-4cf7-8bc0-a5bc92829f46" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_606b6a04-d987-404d-8e98-47d76fd135c4" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember_fd7fd04a-d58c-4cf7-8bc0-a5bc92829f46" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/MarketableSecuritiesSummaryofAvailableforsaleMarketableSecuritiesDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#MarketableSecuritiesSummaryofAvailableforsaleMarketableSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/MarketableSecuritiesSummaryofAvailableforsaleMarketableSecuritiesDetails" xlink:type="extended" id="i1c24372d3c1948bea3b6ef14baddbff9_MarketableSecuritiesSummaryofAvailableforsaleMarketableSecuritiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesLineItems_a1610745-e8c1-453d-9d1a-849c18d00500" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MarketableSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_8b795738-6a55-4733-9bb9-81d44dca92e0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_a1610745-e8c1-453d-9d1a-849c18d00500" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_8b795738-6a55-4733-9bb9-81d44dca92e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_a0a48855-564d-44bf-b49b-c24207a0b0d5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_a1610745-e8c1-453d-9d1a-849c18d00500" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_a0a48855-564d-44bf-b49b-c24207a0b0d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_0650b1bb-b3a8-4e56-88fd-c5dbdec5dcee" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_a1610745-e8c1-453d-9d1a-849c18d00500" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_0650b1bb-b3a8-4e56-88fd-c5dbdec5dcee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_678498ea-3798-43d8-8000-ee9cb41401fb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_a1610745-e8c1-453d-9d1a-849c18d00500" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_678498ea-3798-43d8-8000-ee9cb41401fb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesTable_1a87552a-66f6-43cb-b989-d0837a13cdae" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MarketableSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MarketableSecuritiesLineItems_a1610745-e8c1-453d-9d1a-849c18d00500" xlink:to="loc_us-gaap_MarketableSecuritiesTable_1a87552a-66f6-43cb-b989-d0837a13cdae" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_3bc8860c-4dfb-4483-925b-b7fa56f3f4ba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MarketableSecuritiesTable_1a87552a-66f6-43cb-b989-d0837a13cdae" xlink:to="loc_us-gaap_FinancialInstrumentAxis_3bc8860c-4dfb-4483-925b-b7fa56f3f4ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3bc8860c-4dfb-4483-925b-b7fa56f3f4ba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_3bc8860c-4dfb-4483-925b-b7fa56f3f4ba" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3bc8860c-4dfb-4483-925b-b7fa56f3f4ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ff3ec24b-094f-484f-837a-459e3ea6ac68" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_3bc8860c-4dfb-4483-925b-b7fa56f3f4ba" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ff3ec24b-094f-484f-837a-459e3ea6ac68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_CommercialDebtSecurityMember_3a246ce8-f312-4f67-b2a9-a96ee8b50560" xlink:href="ddog-20220331.xsd#ddog_CommercialDebtSecurityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ff3ec24b-094f-484f-837a-459e3ea6ac68" xlink:to="loc_ddog_CommercialDebtSecurityMember_3a246ce8-f312-4f67-b2a9-a96ee8b50560" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_74e586c1-1878-4ab9-8bbe-5f4faeafd8c5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ff3ec24b-094f-484f-837a-459e3ea6ac68" xlink:to="loc_us-gaap_CertificatesOfDepositMember_74e586c1-1878-4ab9-8bbe-5f4faeafd8c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_d9bea358-a9c8-42d4-90cb-990685359695" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ff3ec24b-094f-484f-837a-459e3ea6ac68" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_d9bea358-a9c8-42d4-90cb-990685359695" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperMember_9d87c600-7f90-4bd3-a372-b4967285849b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommercialPaperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ff3ec24b-094f-484f-837a-459e3ea6ac68" xlink:to="loc_us-gaap_CommercialPaperMember_9d87c600-7f90-4bd3-a372-b4967285849b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_c234cd26-b142-44f8-8647-dd37e18d366e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ff3ec24b-094f-484f-837a-459e3ea6ac68" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_c234cd26-b142-44f8-8647-dd37e18d366e" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/FairValueMeasurementsDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#FairValueMeasurementsDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/FairValueMeasurementsDetails" xlink:type="extended" id="i779e4f9fa24247ada9102a8c9b88695f_FairValueMeasurementsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_21f414de-ea7a-4544-b463-16eb140e435c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_d1dbf479-2cee-415f-a335-1489ca775e55" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_21f414de-ea7a-4544-b463-16eb140e435c" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_d1dbf479-2cee-415f-a335-1489ca775e55" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_f84f946f-628f-4c80-9ea9-829929ef6e84" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_d1dbf479-2cee-415f-a335-1489ca775e55" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_f84f946f-628f-4c80-9ea9-829929ef6e84" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_f4bf3098-b129-4f5d-816d-77fdb8f388e8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_d1dbf479-2cee-415f-a335-1489ca775e55" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_f4bf3098-b129-4f5d-816d-77fdb8f388e8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_5aa08037-3373-4871-852e-d4a8f503d99f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_d1dbf479-2cee-415f-a335-1489ca775e55" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_5aa08037-3373-4871-852e-d4a8f503d99f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_861841f3-e3ae-4bde-b2bd-59eee5e82c04" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_21f414de-ea7a-4544-b463-16eb140e435c" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_861841f3-e3ae-4bde-b2bd-59eee5e82c04" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_e86dd3e1-54a7-42df-ba8f-6dd91f241f40" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_861841f3-e3ae-4bde-b2bd-59eee5e82c04" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_e86dd3e1-54a7-42df-ba8f-6dd91f241f40" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_e86dd3e1-54a7-42df-ba8f-6dd91f241f40_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_e86dd3e1-54a7-42df-ba8f-6dd91f241f40" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_e86dd3e1-54a7-42df-ba8f-6dd91f241f40_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_48faef9c-a459-49d9-87cb-0a9198723c4f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_e86dd3e1-54a7-42df-ba8f-6dd91f241f40" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_48faef9c-a459-49d9-87cb-0a9198723c4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_e7c13d75-f604-4dd2-8b19-38d45d97c4ac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_48faef9c-a459-49d9-87cb-0a9198723c4f" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_e7c13d75-f604-4dd2-8b19-38d45d97c4ac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_395d0df2-35b2-41c5-9bf7-99fa9c133611" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_861841f3-e3ae-4bde-b2bd-59eee5e82c04" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_395d0df2-35b2-41c5-9bf7-99fa9c133611" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_395d0df2-35b2-41c5-9bf7-99fa9c133611_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_395d0df2-35b2-41c5-9bf7-99fa9c133611" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_395d0df2-35b2-41c5-9bf7-99fa9c133611_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_53f7691b-5080-4b94-bdc7-27915e487161" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_395d0df2-35b2-41c5-9bf7-99fa9c133611" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_53f7691b-5080-4b94-bdc7-27915e487161" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_746ef96b-958b-4500-9155-b9627e9f75e5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_53f7691b-5080-4b94-bdc7-27915e487161" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_746ef96b-958b-4500-9155-b9627e9f75e5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_d682dfe3-d92d-4d91-864a-320114660aef" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_53f7691b-5080-4b94-bdc7-27915e487161" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_d682dfe3-d92d-4d91-864a-320114660aef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_af4c19f9-82db-4910-b220-e41fccaeafeb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_53f7691b-5080-4b94-bdc7-27915e487161" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_af4c19f9-82db-4910-b220-e41fccaeafeb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_e03d0ad0-7998-4706-8961-bc713d29a40f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_861841f3-e3ae-4bde-b2bd-59eee5e82c04" xlink:to="loc_us-gaap_FinancialInstrumentAxis_e03d0ad0-7998-4706-8961-bc713d29a40f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e03d0ad0-7998-4706-8961-bc713d29a40f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_e03d0ad0-7998-4706-8961-bc713d29a40f" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e03d0ad0-7998-4706-8961-bc713d29a40f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_593bca66-d9a3-4f49-bf21-101d8bec6a18" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_e03d0ad0-7998-4706-8961-bc713d29a40f" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_593bca66-d9a3-4f49-bf21-101d8bec6a18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_14aa0e13-e555-4363-9749-375332d00d08" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_593bca66-d9a3-4f49-bf21-101d8bec6a18" xlink:to="loc_us-gaap_MoneyMarketFundsMember_14aa0e13-e555-4363-9749-375332d00d08" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperMember_55ecc440-5e59-454d-87de-3bed63391097" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommercialPaperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_593bca66-d9a3-4f49-bf21-101d8bec6a18" xlink:to="loc_us-gaap_CommercialPaperMember_55ecc440-5e59-454d-87de-3bed63391097" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_38dbc786-2a2a-4281-a6ba-6858b0342d45" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_593bca66-d9a3-4f49-bf21-101d8bec6a18" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_38dbc786-2a2a-4281-a6ba-6858b0342d45" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_06805376-c2d5-44e7-bae8-a85519fa542c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_593bca66-d9a3-4f49-bf21-101d8bec6a18" xlink:to="loc_us-gaap_CertificatesOfDepositMember_06805376-c2d5-44e7-bae8-a85519fa542c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryAndGovernmentMember_9889e0da-484c-49e6-b650-c3e574f68bef" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_USTreasuryAndGovernmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_593bca66-d9a3-4f49-bf21-101d8bec6a18" xlink:to="loc_us-gaap_USTreasuryAndGovernmentMember_9889e0da-484c-49e6-b650-c3e574f68bef" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_9f29a9b9-df2d-41e7-8979-81238d8d7b7c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_593bca66-d9a3-4f49-bf21-101d8bec6a18" xlink:to="loc_us-gaap_ForeignGovernmentDebtSecuritiesMember_9f29a9b9-df2d-41e7-8979-81238d8d7b7c" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/PropertyandEquipmentNetComponentsofPropertyandEquipmentNetDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#PropertyandEquipmentNetComponentsofPropertyandEquipmentNetDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/PropertyandEquipmentNetComponentsofPropertyandEquipmentNetDetails" xlink:type="extended" id="i81455f50746e4fafb026c574cd2c02ee_PropertyandEquipmentNetComponentsofPropertyandEquipmentNetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_bd234de0-0eb4-4662-8c53-8f63bb5b6770" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_752fc6b8-89c5-4b11-9d7b-dffb2a7f20e3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_bd234de0-0eb4-4662-8c53-8f63bb5b6770" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_752fc6b8-89c5-4b11-9d7b-dffb2a7f20e3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_379752d6-4c1b-418a-96b1-c5578783e641" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_bd234de0-0eb4-4662-8c53-8f63bb5b6770" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_379752d6-4c1b-418a-96b1-c5578783e641" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_866c145d-aad1-4beb-90ee-97ee4e58fd78" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_bd234de0-0eb4-4662-8c53-8f63bb5b6770" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_866c145d-aad1-4beb-90ee-97ee4e58fd78" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_ea20a61d-4c48-4768-b449-27bac10d7076" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_bd234de0-0eb4-4662-8c53-8f63bb5b6770" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_ea20a61d-4c48-4768-b449-27bac10d7076" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_bbc276b5-f90e-4f59-ac59-45454b2a1c6b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_ea20a61d-4c48-4768-b449-27bac10d7076" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_bbc276b5-f90e-4f59-ac59-45454b2a1c6b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_bbc276b5-f90e-4f59-ac59-45454b2a1c6b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_bbc276b5-f90e-4f59-ac59-45454b2a1c6b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_bbc276b5-f90e-4f59-ac59-45454b2a1c6b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_36165b8f-0b44-4641-83c7-aa794c5efd67" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_bbc276b5-f90e-4f59-ac59-45454b2a1c6b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_36165b8f-0b44-4641-83c7-aa794c5efd67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerEquipmentMember_3fe11f4c-4d94-44f4-aea3-d946cb6b5e73" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ComputerEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_36165b8f-0b44-4641-83c7-aa794c5efd67" xlink:to="loc_us-gaap_ComputerEquipmentMember_3fe11f4c-4d94-44f4-aea3-d946cb6b5e73" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_69ed7fc2-16a1-4dbe-a7b5-af5296ea3dfc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FurnitureAndFixturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_36165b8f-0b44-4641-83c7-aa794c5efd67" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_69ed7fc2-16a1-4dbe-a7b5-af5296ea3dfc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_70b98947-d30a-45db-812d-1dba443421b6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_36165b8f-0b44-4641-83c7-aa794c5efd67" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_70b98947-d30a-45db-812d-1dba443421b6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_f27133ed-45da-4f77-a589-3806e9e77fae" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SoftwareAndSoftwareDevelopmentCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_36165b8f-0b44-4641-83c7-aa794c5efd67" xlink:to="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_f27133ed-45da-4f77-a589-3806e9e77fae" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/AcquisitionsIntangibleAssetsandGoodwillAdditionalInformationDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#AcquisitionsIntangibleAssetsandGoodwillAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/AcquisitionsIntangibleAssetsandGoodwillAdditionalInformationDetails" xlink:type="extended" id="i29c95ac3c4054acf9f7ce2134f2bbba6_AcquisitionsIntangibleAssetsandGoodwillAdditionalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_d80a838e-c27e-4ed4-9392-e13e78f1cf86" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_BusinessCombinationNumber_f3afaee0-9ce3-4deb-82eb-ecc06b19c7b1" xlink:href="ddog-20220331.xsd#ddog_BusinessCombinationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_d80a838e-c27e-4ed4-9392-e13e78f1cf86" xlink:to="loc_ddog_BusinessCombinationNumber_f3afaee0-9ce3-4deb-82eb-ecc06b19c7b1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_c6e23eb4-d185-4830-a6e5-aaab5643e162" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_d80a838e-c27e-4ed4-9392-e13e78f1cf86" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_c6e23eb4-d185-4830-a6e5-aaab5643e162" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_457a11b6-8e79-444d-983b-21a6c0fa01d6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_d80a838e-c27e-4ed4-9392-e13e78f1cf86" xlink:to="loc_us-gaap_Goodwill_457a11b6-8e79-444d-983b-21a6c0fa01d6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_53f3a327-13e6-4acb-8fc3-d864afe2f0e1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_d80a838e-c27e-4ed4-9392-e13e78f1cf86" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_53f3a327-13e6-4acb-8fc3-d864afe2f0e1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_023afddd-60ea-4a1f-b5cb-7ff3752e35ed" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_d80a838e-c27e-4ed4-9392-e13e78f1cf86" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_023afddd-60ea-4a1f-b5cb-7ff3752e35ed" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeveranceCosts1_536d6ba0-e858-4a82-8f41-81422025a502" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SeveranceCosts1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_d80a838e-c27e-4ed4-9392-e13e78f1cf86" xlink:to="loc_us-gaap_SeveranceCosts1_536d6ba0-e858-4a82-8f41-81422025a502" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_71f6bf44-58e5-4828-9a77-d31c66e5ba90" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_d80a838e-c27e-4ed4-9392-e13e78f1cf86" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_71f6bf44-58e5-4828-9a77-d31c66e5ba90" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_72d47b1f-8a7a-4d18-893c-b20b1d3631c6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_d80a838e-c27e-4ed4-9392-e13e78f1cf86" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_72d47b1f-8a7a-4d18-893c-b20b1d3631c6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_d447c129-cafc-4ff4-9d7f-2918746f61d5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_72d47b1f-8a7a-4d18-893c-b20b1d3631c6" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_d447c129-cafc-4ff4-9d7f-2918746f61d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d447c129-cafc-4ff4-9d7f-2918746f61d5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_d447c129-cafc-4ff4-9d7f-2918746f61d5" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d447c129-cafc-4ff4-9d7f-2918746f61d5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d27dcd53-0096-4e27-b0f5-f6b5776d18c2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_d447c129-cafc-4ff4-9d7f-2918746f61d5" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d27dcd53-0096-4e27-b0f5-f6b5776d18c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember_6d809bf1-5678-45a3-8a15-4b8346805360" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d27dcd53-0096-4e27-b0f5-f6b5776d18c2" xlink:to="loc_us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember_6d809bf1-5678-45a3-8a15-4b8346805360" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_AcquisitionInApril2021Member_00ab5ea5-17fe-402d-8389-9bc9d7d1a07a" xlink:href="ddog-20220331.xsd#ddog_AcquisitionInApril2021Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d27dcd53-0096-4e27-b0f5-f6b5776d18c2" xlink:to="loc_ddog_AcquisitionInApril2021Member_00ab5ea5-17fe-402d-8389-9bc9d7d1a07a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_AcquisitionInFebruary2021Member_70a5d08d-77dc-4bee-bd03-d0e8f12af505" xlink:href="ddog-20220331.xsd#ddog_AcquisitionInFebruary2021Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d27dcd53-0096-4e27-b0f5-f6b5776d18c2" xlink:to="loc_ddog_AcquisitionInFebruary2021Member_70a5d08d-77dc-4bee-bd03-d0e8f12af505" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7495a5e1-d188-4cb1-abcc-f4cbed4f7b14" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_72d47b1f-8a7a-4d18-893c-b20b1d3631c6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7495a5e1-d188-4cb1-abcc-f4cbed4f7b14" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7495a5e1-d188-4cb1-abcc-f4cbed4f7b14_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7495a5e1-d188-4cb1-abcc-f4cbed4f7b14" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7495a5e1-d188-4cb1-abcc-f4cbed4f7b14_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ef255269-68d6-4933-9008-d27bace7c59e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7495a5e1-d188-4cb1-abcc-f4cbed4f7b14" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ef255269-68d6-4933-9008-d27bace7c59e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_1c4147b4-6556-4bc6-89f2-b3b1da166919" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ef255269-68d6-4933-9008-d27bace7c59e" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_1c4147b4-6556-4bc6-89f2-b3b1da166919" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_7f412d7d-5eab-4671-849f-5b716c1a4277" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ef255269-68d6-4933-9008-d27bace7c59e" xlink:to="loc_us-gaap_CustomerRelationshipsMember_7f412d7d-5eab-4671-849f-5b716c1a4277" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/AcquisitionsIntangibleAssetsandGoodwillScheduleofIntangibleAssetsNetDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#AcquisitionsIntangibleAssetsandGoodwillScheduleofIntangibleAssetsNetDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/AcquisitionsIntangibleAssetsandGoodwillScheduleofIntangibleAssetsNetDetails" xlink:type="extended" id="i75b185890fea4047bbc763bc76fa1b76_AcquisitionsIntangibleAssetsandGoodwillScheduleofIntangibleAssetsNetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_728ec58e-a10d-46de-bc5f-beaeef34373b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_8ebfd57d-fc20-4552-91e3-75a5192a3729" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_728ec58e-a10d-46de-bc5f-beaeef34373b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_8ebfd57d-fc20-4552-91e3-75a5192a3729" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_f6cef7fa-215e-429a-8083-08e1d0159171" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_728ec58e-a10d-46de-bc5f-beaeef34373b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_f6cef7fa-215e-429a-8083-08e1d0159171" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_fe9f7ee8-c4f5-49f3-b6cb-d452f5c152d8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_728ec58e-a10d-46de-bc5f-beaeef34373b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_fe9f7ee8-c4f5-49f3-b6cb-d452f5c152d8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_35237b91-d623-4140-b9ed-0ae34c1a5fbe" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_728ec58e-a10d-46de-bc5f-beaeef34373b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_35237b91-d623-4140-b9ed-0ae34c1a5fbe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_f027a97b-2ece-45f1-9ee6-6ddea6d0c292" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_728ec58e-a10d-46de-bc5f-beaeef34373b" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_f027a97b-2ece-45f1-9ee6-6ddea6d0c292" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e77968e4-dd87-4b31-b1bc-512753d2ac3e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_f027a97b-2ece-45f1-9ee6-6ddea6d0c292" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e77968e4-dd87-4b31-b1bc-512753d2ac3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e77968e4-dd87-4b31-b1bc-512753d2ac3e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e77968e4-dd87-4b31-b1bc-512753d2ac3e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e77968e4-dd87-4b31-b1bc-512753d2ac3e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a9fc37af-e63a-4ebe-a199-7df4efd205f8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e77968e4-dd87-4b31-b1bc-512753d2ac3e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a9fc37af-e63a-4ebe-a199-7df4efd205f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_b620647e-1f76-4074-92fe-8c6a60bda983" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a9fc37af-e63a-4ebe-a199-7df4efd205f8" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_b620647e-1f76-4074-92fe-8c6a60bda983" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_756c581c-0524-430d-b426-65796e714299" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a9fc37af-e63a-4ebe-a199-7df4efd205f8" xlink:to="loc_us-gaap_CustomerRelationshipsMember_756c581c-0524-430d-b426-65796e714299" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/ConvertibleSeniorNotesAdditionalInformationDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#ConvertibleSeniorNotesAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/ConvertibleSeniorNotesAdditionalInformationDetails" xlink:type="extended" id="i082fd7b8fd7343f4b7e0e94f09ffae3c_ConvertibleSeniorNotesAdditionalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_fe95feaa-672a-45d0-be7e-6e644514908d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_fe95feaa-672a-45d0-be7e-6e644514908d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_058d2c69-2cbc-475d-99e3-9f8b52ffbb1d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_058d2c69-2cbc-475d-99e3-9f8b52ffbb1d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromConvertibleDebt_439a7540-a530-40b2-b58c-3965c0e61c7c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_ProceedsFromConvertibleDebt_439a7540-a530-40b2-b58c-3965c0e61c7c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_bc43de7b-ebe5-464c-92d1-22f8d0df5400" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdTradingDays"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_bc43de7b-ebe5-464c-92d1-22f8d0df5400" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_5adb74b7-c14a-483e-84a8-1e61852bba70" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_5adb74b7-c14a-483e-84a8-1e61852bba70" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_DebtInstrumentConvertibleMeasurementPeriod_662b617c-fa9c-4207-a29a-fa5d23d6f7c9" xlink:href="ddog-20220331.xsd#ddog_DebtInstrumentConvertibleMeasurementPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_ddog_DebtInstrumentConvertibleMeasurementPeriod_662b617c-fa9c-4207-a29a-fa5d23d6f7c9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_57712597-5370-4bbe-8efb-2d3b1278ddab" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_57712597-5370-4bbe-8efb-2d3b1278ddab" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonStock_fca3e40e-f655-4583-90e1-b4747c6479ba" xlink:href="ddog-20220331.xsd#ddog_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_ddog_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonStock_fca3e40e-f655-4583-90e1-b4747c6479ba" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_DebtInstrumentConvertibleThresholdMaximumPercentageOfProductOfLastReportedSalePriceOfCommonStock_cf1e4662-8f34-438a-be2e-a836f04198b4" xlink:href="ddog-20220331.xsd#ddog_DebtInstrumentConvertibleThresholdMaximumPercentageOfProductOfLastReportedSalePriceOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_ddog_DebtInstrumentConvertibleThresholdMaximumPercentageOfProductOfLastReportedSalePriceOfCommonStock_cf1e4662-8f34-438a-be2e-a836f04198b4" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_3d7517d5-1722-467a-a357-c5c40bdf6ceb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionRatio1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_3d7517d5-1722-467a-a357-c5c40bdf6ceb" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_44d8bf74-81de-4daa-bed3-1e0274282ebf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_44d8bf74-81de-4daa-bed3-1e0274282ebf" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_0483f234-6f12-4976-bc4e-f10d362f9e6f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_0483f234-6f12-4976-bc4e-f10d362f9e6f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_DebtInstrumentDiscountForConversionOption_76837b8c-5971-4c73-869b-e8887ea46ec6" xlink:href="ddog-20220331.xsd#ddog_DebtInstrumentDiscountForConversionOption"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_ddog_DebtInstrumentDiscountForConversionOption_76837b8c-5971-4c73-869b-e8887ea46ec6" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_f60a2125-684b-49bb-9e9c-c179933c51cb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_f60a2125-684b-49bb-9e9c-c179933c51cb" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_DebtIssuanceCostAttributableToLiabilityComponent_b41a3a1c-9a98-42d4-a0ea-661f3aa42882" xlink:href="ddog-20220331.xsd#ddog_DebtIssuanceCostAttributableToLiabilityComponent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_ddog_DebtIssuanceCostAttributableToLiabilityComponent_b41a3a1c-9a98-42d4-a0ea-661f3aa42882" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_6c03565e-7482-4f92-bd8c-46f8d5f2d0ce" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_6c03565e-7482-4f92-bd8c-46f8d5f2d0ce" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_DebtIssuanceCostAttributableToEquityComponent_dbe0b29a-cbb9-40fa-8980-e176a4f81152" xlink:href="ddog-20220331.xsd#ddog_DebtIssuanceCostAttributableToEquityComponent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_ddog_DebtIssuanceCostAttributableToEquityComponent_dbe0b29a-cbb9-40fa-8980-e176a4f81152" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_8275ddda-d7d1-474e-a9f1-8350a613f4db" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_StockholdersEquity_8275ddda-d7d1-474e-a9f1-8350a613f4db" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleLongTermNotesPayable_e15c9915-7492-49ae-8707-af4b59078554" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleLongTermNotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_ConvertibleLongTermNotesPayable_e15c9915-7492-49ae-8707-af4b59078554" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_dbd8a9ef-2888-47b9-9dae-46a8e0693d9b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_LongTermDebtFairValue_dbd8a9ef-2888-47b9-9dae-46a8e0693d9b" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleStockPriceTrigger_8697e4f9-bc53-4c59-b4b7-b31fd4b85fcc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleStockPriceTrigger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_DebtInstrumentConvertibleStockPriceTrigger_8697e4f9-bc53-4c59-b4b7-b31fd4b85fcc" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_InitialCapPricePerShareOfCappedCalls_eed8bc7d-07d4-486f-a349-5eae5f016db1" xlink:href="ddog-20220331.xsd#ddog_InitialCapPricePerShareOfCappedCalls"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_ddog_InitialCapPricePerShareOfCappedCalls_eed8bc7d-07d4-486f-a349-5eae5f016db1" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_CommonStockCoveredUnderCappedCallsTransaction_323dbdbc-e9af-41e9-9ae4-6c7ec0a9e2e0" xlink:href="ddog-20220331.xsd#ddog_CommonStockCoveredUnderCappedCallsTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_ddog_CommonStockCoveredUnderCappedCallsTransaction_323dbdbc-e9af-41e9-9ae4-6c7ec0a9e2e0" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_CostIncurredToPurchaseCappedCalls_10e7daea-80c8-4586-9fde-79f15959d370" xlink:href="ddog-20220331.xsd#ddog_CostIncurredToPurchaseCappedCalls"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_ddog_CostIncurredToPurchaseCappedCalls_10e7daea-80c8-4586-9fde-79f15959d370" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_661b9eb4-ad4b-4b9b-8464-17e3ff7b62c5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_6cf8afb0-cd64-4429-9edf-b68603f254e6" xlink:to="loc_us-gaap_DebtInstrumentTable_661b9eb4-ad4b-4b9b-8464-17e3ff7b62c5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_f2c104ad-3213-4f1d-995e-8e4a0d4c925e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_661b9eb4-ad4b-4b9b-8464-17e3ff7b62c5" xlink:to="loc_us-gaap_DebtInstrumentAxis_f2c104ad-3213-4f1d-995e-8e4a0d4c925e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_f2c104ad-3213-4f1d-995e-8e4a0d4c925e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_f2c104ad-3213-4f1d-995e-8e4a0d4c925e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_f2c104ad-3213-4f1d-995e-8e4a0d4c925e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ba7bbdd0-298f-476c-94ad-787b0651e43d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_f2c104ad-3213-4f1d-995e-8e4a0d4c925e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ba7bbdd0-298f-476c-94ad-787b0651e43d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_A0125ConvertibleSeniorNotesDue2025Member_8372b742-9bfb-4770-afd3-4dfd252547a1" xlink:href="ddog-20220331.xsd#ddog_A0125ConvertibleSeniorNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ba7bbdd0-298f-476c-94ad-787b0651e43d" xlink:to="loc_ddog_A0125ConvertibleSeniorNotesDue2025Member_8372b742-9bfb-4770-afd3-4dfd252547a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_185e11f0-3e0b-4cb1-85ed-e38c7c1d50c3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_661b9eb4-ad4b-4b9b-8464-17e3ff7b62c5" xlink:to="loc_us-gaap_StatementClassOfStockAxis_185e11f0-3e0b-4cb1-85ed-e38c7c1d50c3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_185e11f0-3e0b-4cb1-85ed-e38c7c1d50c3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_185e11f0-3e0b-4cb1-85ed-e38c7c1d50c3" xlink:to="loc_us-gaap_ClassOfStockDomain_185e11f0-3e0b-4cb1-85ed-e38c7c1d50c3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_66be3233-0a22-4bf7-accb-a0933b24f7e1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_185e11f0-3e0b-4cb1-85ed-e38c7c1d50c3" xlink:to="loc_us-gaap_ClassOfStockDomain_66be3233-0a22-4bf7-accb-a0933b24f7e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_47d690a3-7fad-4ff6-98f3-cfb88d6f1bb5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_66be3233-0a22-4bf7-accb-a0933b24f7e1" xlink:to="loc_us-gaap_CommonClassAMember_47d690a3-7fad-4ff6-98f3-cfb88d6f1bb5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_fddf1196-f958-49a9-954a-08150026fd65" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_661b9eb4-ad4b-4b9b-8464-17e3ff7b62c5" xlink:to="loc_srt_RangeAxis_fddf1196-f958-49a9-954a-08150026fd65" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_fddf1196-f958-49a9-954a-08150026fd65_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_fddf1196-f958-49a9-954a-08150026fd65" xlink:to="loc_srt_RangeMember_fddf1196-f958-49a9-954a-08150026fd65_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_c604f3e1-8b83-4879-b3f9-acd5457e0634" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_fddf1196-f958-49a9-954a-08150026fd65" xlink:to="loc_srt_RangeMember_c604f3e1-8b83-4879-b3f9-acd5457e0634" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_06e5afe7-7172-4d89-90c4-38e0b0c99c47" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c604f3e1-8b83-4879-b3f9-acd5457e0634" xlink:to="loc_srt_MinimumMember_06e5afe7-7172-4d89-90c4-38e0b0c99c47" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_540c095d-64a2-4d96-940d-d9a946452ba5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_661b9eb4-ad4b-4b9b-8464-17e3ff7b62c5" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_540c095d-64a2-4d96-940d-d9a946452ba5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_540c095d-64a2-4d96-940d-d9a946452ba5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_540c095d-64a2-4d96-940d-d9a946452ba5" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_540c095d-64a2-4d96-940d-d9a946452ba5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_ce955387-3ce6-4149-9112-77c2cd1d6e27" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_540c095d-64a2-4d96-940d-d9a946452ba5" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_ce955387-3ce6-4149-9112-77c2cd1d6e27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_4c479f47-8444-459e-a54c-ea8303fbbffc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_ce955387-3ce6-4149-9112-77c2cd1d6e27" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_4c479f47-8444-459e-a54c-ea8303fbbffc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_DebtInstrumentConvertibleTermsAxis_8c0862c5-f20e-4152-852e-e77341407812" xlink:href="ddog-20220331.xsd#ddog_DebtInstrumentConvertibleTermsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_661b9eb4-ad4b-4b9b-8464-17e3ff7b62c5" xlink:to="loc_ddog_DebtInstrumentConvertibleTermsAxis_8c0862c5-f20e-4152-852e-e77341407812" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_DebtInstrumentConvertibleTermsDomain_8c0862c5-f20e-4152-852e-e77341407812_default" xlink:href="ddog-20220331.xsd#ddog_DebtInstrumentConvertibleTermsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_ddog_DebtInstrumentConvertibleTermsAxis_8c0862c5-f20e-4152-852e-e77341407812" xlink:to="loc_ddog_DebtInstrumentConvertibleTermsDomain_8c0862c5-f20e-4152-852e-e77341407812_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_DebtInstrumentConvertibleTermsDomain_1711c349-b861-4ff9-8fda-1ba69207ddbd" xlink:href="ddog-20220331.xsd#ddog_DebtInstrumentConvertibleTermsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_ddog_DebtInstrumentConvertibleTermsAxis_8c0862c5-f20e-4152-852e-e77341407812" xlink:to="loc_ddog_DebtInstrumentConvertibleTermsDomain_1711c349-b861-4ff9-8fda-1ba69207ddbd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_ScenarioOneMember_a3a53eae-cda6-4a5b-849c-8c4e0935b95c" xlink:href="ddog-20220331.xsd#ddog_ScenarioOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ddog_DebtInstrumentConvertibleTermsDomain_1711c349-b861-4ff9-8fda-1ba69207ddbd" xlink:to="loc_ddog_ScenarioOneMember_a3a53eae-cda6-4a5b-849c-8c4e0935b95c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_ScenarioTwoMember_4e0b2d0a-8d82-434e-8956-4e277e5748bd" xlink:href="ddog-20220331.xsd#ddog_ScenarioTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ddog_DebtInstrumentConvertibleTermsDomain_1711c349-b861-4ff9-8fda-1ba69207ddbd" xlink:to="loc_ddog_ScenarioTwoMember_4e0b2d0a-8d82-434e-8956-4e277e5748bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_ScenarioThreeMember_9c2ab79d-77c4-47c8-9c2e-e646f7f3150a" xlink:href="ddog-20220331.xsd#ddog_ScenarioThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ddog_DebtInstrumentConvertibleTermsDomain_1711c349-b861-4ff9-8fda-1ba69207ddbd" xlink:to="loc_ddog_ScenarioThreeMember_9c2ab79d-77c4-47c8-9c2e-e646f7f3150a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_5468c60f-49ff-4bff-b077-d973c3b4fb8d" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_661b9eb4-ad4b-4b9b-8464-17e3ff7b62c5" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_5468c60f-49ff-4bff-b077-d973c3b4fb8d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_5468c60f-49ff-4bff-b077-d973c3b4fb8d_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_5468c60f-49ff-4bff-b077-d973c3b4fb8d" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_5468c60f-49ff-4bff-b077-d973c3b4fb8d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_2e64bd3b-5b00-48dc-bfe8-a1e892580b94" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_5468c60f-49ff-4bff-b077-d973c3b4fb8d" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_2e64bd3b-5b00-48dc-bfe8-a1e892580b94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_3a771248-1fef-43e5-b6cc-f3a03f2a9aae" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_2e64bd3b-5b00-48dc-bfe8-a1e892580b94" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_3a771248-1fef-43e5-b6cc-f3a03f2a9aae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_ffc2617f-4f1b-4e2b-9775-f04c11e09a2f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_661b9eb4-ad4b-4b9b-8464-17e3ff7b62c5" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_ffc2617f-4f1b-4e2b-9775-f04c11e09a2f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfAdoptionMember_ffc2617f-4f1b-4e2b-9775-f04c11e09a2f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TypeOfAdoptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_ffc2617f-4f1b-4e2b-9775-f04c11e09a2f" xlink:to="loc_us-gaap_TypeOfAdoptionMember_ffc2617f-4f1b-4e2b-9775-f04c11e09a2f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfAdoptionMember_216f7f31-251f-4554-a04e-c08d119708c8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TypeOfAdoptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_ffc2617f-4f1b-4e2b-9775-f04c11e09a2f" xlink:to="loc_us-gaap_TypeOfAdoptionMember_216f7f31-251f-4554-a04e-c08d119708c8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountingStandardsUpdate202006Member_36ba2427-5dcb-4f5e-8ff3-ce32b45ad260" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountingStandardsUpdate202006Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_216f7f31-251f-4554-a04e-c08d119708c8" xlink:to="loc_us-gaap_AccountingStandardsUpdate202006Member_36ba2427-5dcb-4f5e-8ff3-ce32b45ad260" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_88de922e-c100-484a-b067-abc4b12cb57d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_661b9eb4-ad4b-4b9b-8464-17e3ff7b62c5" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_88de922e-c100-484a-b067-abc4b12cb57d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_88de922e-c100-484a-b067-abc4b12cb57d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_88de922e-c100-484a-b067-abc4b12cb57d" xlink:to="loc_us-gaap_EquityComponentDomain_88de922e-c100-484a-b067-abc4b12cb57d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_cad65127-8571-40a1-b05e-8ac7f2aec0ea" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_88de922e-c100-484a-b067-abc4b12cb57d" xlink:to="loc_us-gaap_EquityComponentDomain_cad65127-8571-40a1-b05e-8ac7f2aec0ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_f6bc920e-a0a8-44d0-9362-6d4c9510f35f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_cad65127-8571-40a1-b05e-8ac7f2aec0ea" xlink:to="loc_us-gaap_RetainedEarningsMember_f6bc920e-a0a8-44d0-9362-6d4c9510f35f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_6e35046e-9b2a-46d2-ad8d-c3785f88a112" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_cad65127-8571-40a1-b05e-8ac7f2aec0ea" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_6e35046e-9b2a-46d2-ad8d-c3785f88a112" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/ConvertibleSeniorNotesSummaryofNetCarryingAmountofLiabilityComponentof2025NotesDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#ConvertibleSeniorNotesSummaryofNetCarryingAmountofLiabilityComponentof2025NotesDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/ConvertibleSeniorNotesSummaryofNetCarryingAmountofLiabilityComponentof2025NotesDetails" xlink:type="extended" id="ided17b1eca1b4d009cbf77b5e4f9f236_ConvertibleSeniorNotesSummaryofNetCarryingAmountofLiabilityComponentof2025NotesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_38ead711-b83f-4e0e-b237-1317b64beec8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_7f672e27-520d-49ab-81fe-a9bd05f31564" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38ead711-b83f-4e0e-b237-1317b64beec8" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_7f672e27-520d-49ab-81fe-a9bd05f31564" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_fcd096b8-2af4-4ace-bf46-9131942991de" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_UnamortizedDebtIssuanceExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38ead711-b83f-4e0e-b237-1317b64beec8" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_fcd096b8-2af4-4ace-bf46-9131942991de" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleLongTermNotesPayable_03186472-ad03-4ac2-9732-25dd90d1d5a0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleLongTermNotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38ead711-b83f-4e0e-b237-1317b64beec8" xlink:to="loc_us-gaap_ConvertibleLongTermNotesPayable_03186472-ad03-4ac2-9732-25dd90d1d5a0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_c8a914f1-2d67-4e1c-80f3-5e36303a8fc9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_38ead711-b83f-4e0e-b237-1317b64beec8" xlink:to="loc_us-gaap_DebtInstrumentTable_c8a914f1-2d67-4e1c-80f3-5e36303a8fc9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_6556eb41-4ea0-4b56-91d2-e1221cae8dc1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c8a914f1-2d67-4e1c-80f3-5e36303a8fc9" xlink:to="loc_us-gaap_DebtInstrumentAxis_6556eb41-4ea0-4b56-91d2-e1221cae8dc1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_6556eb41-4ea0-4b56-91d2-e1221cae8dc1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_6556eb41-4ea0-4b56-91d2-e1221cae8dc1" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_6556eb41-4ea0-4b56-91d2-e1221cae8dc1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_2f625da7-50cb-4fc2-8b57-a89d09118bda" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_6556eb41-4ea0-4b56-91d2-e1221cae8dc1" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_2f625da7-50cb-4fc2-8b57-a89d09118bda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_A0125ConvertibleSeniorNotesDue2025Member_1e257949-996f-4bec-9204-71630a62df0f" xlink:href="ddog-20220331.xsd#ddog_A0125ConvertibleSeniorNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_2f625da7-50cb-4fc2-8b57-a89d09118bda" xlink:to="loc_ddog_A0125ConvertibleSeniorNotesDue2025Member_1e257949-996f-4bec-9204-71630a62df0f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/ConvertibleSeniorNotesInterestExpenserelatedto2025NotesDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#ConvertibleSeniorNotesInterestExpenserelatedto2025NotesDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/ConvertibleSeniorNotesInterestExpenserelatedto2025NotesDetails" xlink:type="extended" id="i5803f716d4fb4f028b57dcd81fa28d84_ConvertibleSeniorNotesInterestExpenserelatedto2025NotesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_a9683e8d-1c95-459b-98a5-dc8765c6261f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebtExcludingAmortization_e4e55f8b-1374-426e-87f6-55fa07cd8517" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestExpenseDebtExcludingAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a9683e8d-1c95-459b-98a5-dc8765c6261f" xlink:to="loc_us-gaap_InterestExpenseDebtExcludingAmortization_e4e55f8b-1374-426e-87f6-55fa07cd8517" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_a2d33e18-42a5-469c-ae78-e5d083c01b58" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a9683e8d-1c95-459b-98a5-dc8765c6261f" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_a2d33e18-42a5-469c-ae78-e5d083c01b58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_a84d48c9-f6a1-4769-9dc3-7758516eb47d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a9683e8d-1c95-459b-98a5-dc8765c6261f" xlink:to="loc_us-gaap_InterestExpenseDebt_a84d48c9-f6a1-4769-9dc3-7758516eb47d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_5f1e4f29-b7b3-475d-9822-28a22ae24d32" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_a9683e8d-1c95-459b-98a5-dc8765c6261f" xlink:to="loc_us-gaap_DebtInstrumentTable_5f1e4f29-b7b3-475d-9822-28a22ae24d32" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_6cb674ef-d8e6-4002-8a96-918d52cdb885" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_5f1e4f29-b7b3-475d-9822-28a22ae24d32" xlink:to="loc_us-gaap_DebtInstrumentAxis_6cb674ef-d8e6-4002-8a96-918d52cdb885" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_6cb674ef-d8e6-4002-8a96-918d52cdb885_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_6cb674ef-d8e6-4002-8a96-918d52cdb885" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_6cb674ef-d8e6-4002-8a96-918d52cdb885_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_bc8aa7ea-7e8f-4a7a-bfa0-7dcd52c2066f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_6cb674ef-d8e6-4002-8a96-918d52cdb885" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_bc8aa7ea-7e8f-4a7a-bfa0-7dcd52c2066f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_A0125ConvertibleSeniorNotesDue2025Member_d4292623-24e0-4bfb-bee0-8e72a9c4fbb9" xlink:href="ddog-20220331.xsd#ddog_A0125ConvertibleSeniorNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_bc8aa7ea-7e8f-4a7a-bfa0-7dcd52c2066f" xlink:to="loc_ddog_A0125ConvertibleSeniorNotesDue2025Member_d4292623-24e0-4bfb-bee0-8e72a9c4fbb9" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/RevenueScheduleofRevenuebyGeographicAreaDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#RevenueScheduleofRevenuebyGeographicAreaDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/RevenueScheduleofRevenuebyGeographicAreaDetails" xlink:type="extended" id="i90fd2b27f0a44f6c907ef93a7cb4bd7e_RevenueScheduleofRevenuebyGeographicAreaDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_bb559392-235f-4db9-80ed-bb1babec7cda" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_98ca52ca-38f4-4cf6-a41f-2adc8590d6cd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_bb559392-235f-4db9-80ed-bb1babec7cda" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_98ca52ca-38f4-4cf6-a41f-2adc8590d6cd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_81080d34-3ced-4f83-8eab-b67382311cf3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_bb559392-235f-4db9-80ed-bb1babec7cda" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_81080d34-3ced-4f83-8eab-b67382311cf3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_30df9763-4ee1-49e2-a1f8-4e3e964575f3" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_81080d34-3ced-4f83-8eab-b67382311cf3" xlink:to="loc_srt_StatementGeographicalAxis_30df9763-4ee1-49e2-a1f8-4e3e964575f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_30df9763-4ee1-49e2-a1f8-4e3e964575f3_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_30df9763-4ee1-49e2-a1f8-4e3e964575f3" xlink:to="loc_srt_SegmentGeographicalDomain_30df9763-4ee1-49e2-a1f8-4e3e964575f3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_363984ec-ed1e-4f23-8e4e-728e5428af7b" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_30df9763-4ee1-49e2-a1f8-4e3e964575f3" xlink:to="loc_srt_SegmentGeographicalDomain_363984ec-ed1e-4f23-8e4e-728e5428af7b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NorthAmericaMember_cbc11dc0-dc1b-4325-8ff9-049b5e252481" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_NorthAmericaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_363984ec-ed1e-4f23-8e4e-728e5428af7b" xlink:to="loc_srt_NorthAmericaMember_cbc11dc0-dc1b-4325-8ff9-049b5e252481" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_InternationalMember_078f4f68-b516-4264-ab78-fdbc6a1f1f11" xlink:href="ddog-20220331.xsd#ddog_InternationalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_363984ec-ed1e-4f23-8e4e-728e5428af7b" xlink:to="loc_ddog_InternationalMember_078f4f68-b516-4264-ab78-fdbc6a1f1f11" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/RevenueRevenueRemainingPerformanceObligationDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#RevenueRevenueRemainingPerformanceObligationDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/RevenueRevenueRemainingPerformanceObligationDetails" xlink:type="extended" id="ia7136cb0094d47acbfab74d452e15aa4_RevenueRevenueRemainingPerformanceObligationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5b8639bd-31c3-4e7e-af40-6dd3d1186370" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_a5322fae-3cfb-479d-8cc2-3c62a97a2eb4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5b8639bd-31c3-4e7e-af40-6dd3d1186370" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_a5322fae-3cfb-479d-8cc2-3c62a97a2eb4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_afb2b9da-fbd7-45b9-aec3-09df8f627ca8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5b8639bd-31c3-4e7e-af40-6dd3d1186370" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_afb2b9da-fbd7-45b9-aec3-09df8f627ca8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_adca6fe9-13cc-4b4e-a4a0-e89b72f96fb3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5b8639bd-31c3-4e7e-af40-6dd3d1186370" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_adca6fe9-13cc-4b4e-a4a0-e89b72f96fb3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_bb271e81-e3f3-4cc2-95a8-6fa256f63174" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_adca6fe9-13cc-4b4e-a4a0-e89b72f96fb3" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_bb271e81-e3f3-4cc2-95a8-6fa256f63174" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/RevenueRevenueRemainingPerformanceObligationDetails_1" xlink:type="simple" xlink:href="ddog-20220331.xsd#RevenueRevenueRemainingPerformanceObligationDetails_1"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/RevenueRevenueRemainingPerformanceObligationDetails_1" xlink:type="extended" id="if5a6eb805eb84b41a49e971da6936c89_RevenueRevenueRemainingPerformanceObligationDetails_1">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5b8639bd-31c3-4e7e-af40-6dd3d1186370" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_a5322fae-3cfb-479d-8cc2-3c62a97a2eb4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5b8639bd-31c3-4e7e-af40-6dd3d1186370" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_a5322fae-3cfb-479d-8cc2-3c62a97a2eb4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_afb2b9da-fbd7-45b9-aec3-09df8f627ca8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5b8639bd-31c3-4e7e-af40-6dd3d1186370" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_afb2b9da-fbd7-45b9-aec3-09df8f627ca8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_adca6fe9-13cc-4b4e-a4a0-e89b72f96fb3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5b8639bd-31c3-4e7e-af40-6dd3d1186370" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_adca6fe9-13cc-4b4e-a4a0-e89b72f96fb3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/StockholdersEquityAdditionalInformationDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#StockholdersEquityAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/StockholdersEquityAdditionalInformationDetails" xlink:type="extended" id="i3067e0bad7584f038bf9373aeb035122_StockholdersEquityAdditionalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_NumberOfCommonStockClasses_97412ad0-5f3f-4d48-9bb6-ad744476272f" xlink:href="ddog-20220331.xsd#ddog_NumberOfCommonStockClasses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_ddog_NumberOfCommonStockClasses_97412ad0-5f3f-4d48-9bb6-ad744476272f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_NumberOfVotingRightsEntitledToStockholdersPerShare_8a58bc2e-0725-42f8-b1cf-c29ce717b5a6" xlink:href="ddog-20220331.xsd#ddog_NumberOfVotingRightsEntitledToStockholdersPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_ddog_NumberOfVotingRightsEntitledToStockholdersPerShare_8a58bc2e-0725-42f8-b1cf-c29ce717b5a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConversionOfStockSharesConverted1_18006d0b-2922-4350-8f90-5c4056980c90" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConversionOfStockSharesConverted1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_ConversionOfStockSharesConverted1_18006d0b-2922-4350-8f90-5c4056980c90" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_65c5481f-9de8-4076-90e2-9114f27bf9b5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_65c5481f-9de8-4076-90e2-9114f27bf9b5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_271c17d8-e3c6-41d2-9e8c-debb11911966" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_271c17d8-e3c6-41d2-9e8c-debb11911966" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_fe6f2713-0dd1-4452-b6ca-cdc304fd5c23" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_CommonStockSharesIssued_fe6f2713-0dd1-4452-b6ca-cdc304fd5c23" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_8c018212-9578-4de6-aafe-866900eeac94" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_8c018212-9578-4de6-aafe-866900eeac94" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfEquityIncentivePlan_ea662cf5-4082-4b50-a0f7-070e4fd0c663" xlink:href="ddog-20220331.xsd#ddog_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfEquityIncentivePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_ddog_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfEquityIncentivePlan_ea662cf5-4082-4b50-a0f7-070e4fd0c663" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_844fc4ef-59d6-4499-ba2a-63d444de4804" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_844fc4ef-59d6-4499-ba2a-63d444de4804" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_c42a976c-0725-4503-b5fe-32608c72b663" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_c42a976c-0725-4503-b5fe-32608c72b663" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_b5f54f35-ec8a-47c3-a62d-179f954eea40" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_b5f54f35-ec8a-47c3-a62d-179f954eea40" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_75219d2f-507a-4e1f-a5f1-0e4b90311413" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_75219d2f-507a-4e1f-a5f1-0e4b90311413" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_611d5ac2-959f-46d2-aff2-a9f3559d3738" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_611d5ac2-959f-46d2-aff2-a9f3559d3738" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_5ffd59cb-dc1f-40ed-8f88-f6323a219a8b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_5ffd59cb-dc1f-40ed-8f88-f6323a219a8b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_db7a9507-176d-43ca-aeb4-c53bffdea34a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_db7a9507-176d-43ca-aeb4-c53bffdea34a" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_a1d92263-bd9e-4ff6-a146-074efb8eca0a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_a1d92263-bd9e-4ff6-a146-074efb8eca0a" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_CommonStockIssuedSubjectToRepurchaseRelatedToEarlyExerciseOfOptions_2f2a82da-586e-4540-b95c-1ba3a4b5ab2b" xlink:href="ddog-20220331.xsd#ddog_CommonStockIssuedSubjectToRepurchaseRelatedToEarlyExerciseOfOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_ddog_CommonStockIssuedSubjectToRepurchaseRelatedToEarlyExerciseOfOptions_2f2a82da-586e-4540-b95c-1ba3a4b5ab2b" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_1a885b74-8f53-4f49-9a7e-c253e0d30fb3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_1a885b74-8f53-4f49-9a7e-c253e0d30fb3" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_961d5c9c-cf47-4e4c-9c92-8d842b6a6fed" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_961d5c9c-cf47-4e4c-9c92-8d842b6a6fed" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_10360802-5705-4d5a-91a3-ad34562a24b3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_10360802-5705-4d5a-91a3-ad34562a24b3" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_7c68d025-1941-45d7-885f-126c47e0262a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_7c68d025-1941-45d7-885f-126c47e0262a" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_EmployeeStockPurchasePlansPurchasePricePercentage_5e2dbdf0-31c5-4ebc-b0cb-b6caefac87f6" xlink:href="ddog-20220331.xsd#ddog_EmployeeStockPurchasePlansPurchasePricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_ddog_EmployeeStockPurchasePlansPurchasePricePercentage_5e2dbdf0-31c5-4ebc-b0cb-b6caefac87f6" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_6be74f1e-c057-4e80-b33b-57db2f8f0c0a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_6be74f1e-c057-4e80-b33b-57db2f8f0c0a" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_71e2529d-7bb4-4c9c-b0f9-44abb908fd3e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_71e2529d-7bb4-4c9c-b0f9-44abb908fd3e" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7eabecf3-dced-4170-a709-671474875876" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e93878f6-89fd-480c-aa82-9cadee3b13e9" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7eabecf3-dced-4170-a709-671474875876" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_e98957da-583a-45b0-b0a1-29ebcdb04420" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7eabecf3-dced-4170-a709-671474875876" xlink:to="loc_us-gaap_StatementClassOfStockAxis_e98957da-583a-45b0-b0a1-29ebcdb04420" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_e98957da-583a-45b0-b0a1-29ebcdb04420_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_e98957da-583a-45b0-b0a1-29ebcdb04420" xlink:to="loc_us-gaap_ClassOfStockDomain_e98957da-583a-45b0-b0a1-29ebcdb04420_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_8ce6fa72-67cf-4e38-94f4-1923b9c1a6d9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_e98957da-583a-45b0-b0a1-29ebcdb04420" xlink:to="loc_us-gaap_ClassOfStockDomain_8ce6fa72-67cf-4e38-94f4-1923b9c1a6d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_e1c8c14f-0667-47cf-bdf2-e1950f779df9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_8ce6fa72-67cf-4e38-94f4-1923b9c1a6d9" xlink:to="loc_us-gaap_CommonClassAMember_e1c8c14f-0667-47cf-bdf2-e1950f779df9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_86f13014-cb2e-4f0d-8962-6989bd4df5f7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_8ce6fa72-67cf-4e38-94f4-1923b9c1a6d9" xlink:to="loc_us-gaap_CommonClassBMember_86f13014-cb2e-4f0d-8962-6989bd4df5f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_a9438b75-0924-4dd6-985e-0fa60596fb35" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7eabecf3-dced-4170-a709-671474875876" xlink:to="loc_us-gaap_PlanNameAxis_a9438b75-0924-4dd6-985e-0fa60596fb35" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_a9438b75-0924-4dd6-985e-0fa60596fb35_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_a9438b75-0924-4dd6-985e-0fa60596fb35" xlink:to="loc_us-gaap_PlanNameDomain_a9438b75-0924-4dd6-985e-0fa60596fb35_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_bcccefa9-4ccf-4b43-8bb4-991133e005a2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_a9438b75-0924-4dd6-985e-0fa60596fb35" xlink:to="loc_us-gaap_PlanNameDomain_bcccefa9-4ccf-4b43-8bb4-991133e005a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_TwoThousandNineteenEquityIncentivePlanMember_c4d78c86-46f3-44a8-8991-f93718b73758" xlink:href="ddog-20220331.xsd#ddog_TwoThousandNineteenEquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_bcccefa9-4ccf-4b43-8bb4-991133e005a2" xlink:to="loc_ddog_TwoThousandNineteenEquityIncentivePlanMember_c4d78c86-46f3-44a8-8991-f93718b73758" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_EmployeeStockPurchasePlanMember_8b798d85-d67a-4047-b1d8-b7f53ca1a7c1" xlink:href="ddog-20220331.xsd#ddog_EmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_bcccefa9-4ccf-4b43-8bb4-991133e005a2" xlink:to="loc_ddog_EmployeeStockPurchasePlanMember_8b798d85-d67a-4047-b1d8-b7f53ca1a7c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_7527e307-a2e3-4136-b7f3-dffafa963c2f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_7eabecf3-dced-4170-a709-671474875876" xlink:to="loc_us-gaap_AwardTypeAxis_7527e307-a2e3-4136-b7f3-dffafa963c2f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7527e307-a2e3-4136-b7f3-dffafa963c2f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_7527e307-a2e3-4136-b7f3-dffafa963c2f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7527e307-a2e3-4136-b7f3-dffafa963c2f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c405e0cb-784c-4eb8-9c32-9e30368d6218" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_7527e307-a2e3-4136-b7f3-dffafa963c2f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c405e0cb-784c-4eb8-9c32-9e30368d6218" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_ac4e8ffc-94d8-4506-b047-499406de0421" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c405e0cb-784c-4eb8-9c32-9e30368d6218" xlink:to="loc_us-gaap_EmployeeStockOptionMember_ac4e8ffc-94d8-4506-b047-499406de0421" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_e6e7131c-9a39-4b6f-91cf-06c63f6234b0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c405e0cb-784c-4eb8-9c32-9e30368d6218" xlink:to="loc_us-gaap_PerformanceSharesMember_e6e7131c-9a39-4b6f-91cf-06c63f6234b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_33a07d35-b509-435a-ac66-8f7521c54274" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c405e0cb-784c-4eb8-9c32-9e30368d6218" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_33a07d35-b509-435a-ac66-8f7521c54274" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/StockholdersEquitySummaryofActivityforUnvestedRSUsDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#StockholdersEquitySummaryofActivityforUnvestedRSUsDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/StockholdersEquitySummaryofActivityforUnvestedRSUsDetails" xlink:type="extended" id="i13adc1cc43134081974ae9a78e41f4a3_StockholdersEquitySummaryofActivityforUnvestedRSUsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_902fa7b2-b8f2-4d8d-840b-ee23031db549" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d0235f04-68dd-4a46-9fd3-b20bd775ea6d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_902fa7b2-b8f2-4d8d-840b-ee23031db549" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d0235f04-68dd-4a46-9fd3-b20bd775ea6d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_85a03be6-ee3b-4d67-8d94-1c8c8d824830" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d0235f04-68dd-4a46-9fd3-b20bd775ea6d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_85a03be6-ee3b-4d67-8d94-1c8c8d824830" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_4fb08f05-3ac4-45b4-a965-6ded56468743" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d0235f04-68dd-4a46-9fd3-b20bd775ea6d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_4fb08f05-3ac4-45b4-a965-6ded56468743" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_fffe6ab4-cf72-4049-881c-3fb950e9df76" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d0235f04-68dd-4a46-9fd3-b20bd775ea6d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_fffe6ab4-cf72-4049-881c-3fb950e9df76" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_46778848-860d-4510-9b02-9e30fba740af" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d0235f04-68dd-4a46-9fd3-b20bd775ea6d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_46778848-860d-4510-9b02-9e30fba740af" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_8a16a181-f957-4a93-8b38-9a55649f3835" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_e4df5e33-3f5d-4eb5-8d0c-8be13b616cf6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_902fa7b2-b8f2-4d8d-840b-ee23031db549" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_e4df5e33-3f5d-4eb5-8d0c-8be13b616cf6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_7b1495f9-6ae2-4d5f-8f44-35859af74ef7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_e4df5e33-3f5d-4eb5-8d0c-8be13b616cf6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_7b1495f9-6ae2-4d5f-8f44-35859af74ef7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_bfb93eea-30c0-4b25-88dc-6331d7f3b7a7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_e4df5e33-3f5d-4eb5-8d0c-8be13b616cf6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_bfb93eea-30c0-4b25-88dc-6331d7f3b7a7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_9c2d1903-12d4-49c4-9f54-e63d7e5db3bd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_e4df5e33-3f5d-4eb5-8d0c-8be13b616cf6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_9c2d1903-12d4-49c4-9f54-e63d7e5db3bd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_10b7c67f-a5e0-4834-a505-5dea76fc8187" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_e4df5e33-3f5d-4eb5-8d0c-8be13b616cf6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_10b7c67f-a5e0-4834-a505-5dea76fc8187" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_9bb8f97e-bd40-4822-96da-243fc1a41b5d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_13adc948-da8e-4ccc-82ed-f6985706edbb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_902fa7b2-b8f2-4d8d-840b-ee23031db549" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_13adc948-da8e-4ccc-82ed-f6985706edbb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_6a12cadf-3d43-4ddf-a649-0166e83a6e06" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_13adc948-da8e-4ccc-82ed-f6985706edbb" xlink:to="loc_us-gaap_AwardTypeAxis_6a12cadf-3d43-4ddf-a649-0166e83a6e06" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6a12cadf-3d43-4ddf-a649-0166e83a6e06_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_6a12cadf-3d43-4ddf-a649-0166e83a6e06" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6a12cadf-3d43-4ddf-a649-0166e83a6e06_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_235e58ec-81c7-4768-a133-4fd81b38d2e6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_6a12cadf-3d43-4ddf-a649-0166e83a6e06" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_235e58ec-81c7-4768-a133-4fd81b38d2e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_4edd5437-f36c-4232-ba34-f7e8b88a46cc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_235e58ec-81c7-4768-a133-4fd81b38d2e6" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_4edd5437-f36c-4232-ba34-f7e8b88a46cc" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/StockholdersEquitySummaryofStockbasedCompensationExpenseDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#StockholdersEquitySummaryofStockbasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/StockholdersEquitySummaryofStockbasedCompensationExpenseDetails" xlink:type="extended" id="i141c306e1f4a4a08b81ffee1fb30aedd_StockholdersEquitySummaryofStockbasedCompensationExpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_b37fe9fe-4103-4e82-952b-9461b98030a1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_ea4780e9-1fd7-4811-9a68-4ee600ad4d5a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_b37fe9fe-4103-4e82-952b-9461b98030a1" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_ea4780e9-1fd7-4811-9a68-4ee600ad4d5a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount_6eee8aed-2d9f-4403-9d9e-bdc4b93f1b5f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_b37fe9fe-4103-4e82-952b-9461b98030a1" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount_6eee8aed-2d9f-4403-9d9e-bdc4b93f1b5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardCompensationCost1_d4ff0369-021d-4dd4-a81c-af22e20b11fd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardCompensationCost1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_b37fe9fe-4103-4e82-952b-9461b98030a1" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardCompensationCost1_d4ff0369-021d-4dd4-a81c-af22e20b11fd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_2132728c-828f-4b78-bdea-3d876cdbe61d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_b37fe9fe-4103-4e82-952b-9461b98030a1" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_2132728c-828f-4b78-bdea-3d876cdbe61d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_62cc75f0-0946-463e-a8bb-431dfb21396c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_2132728c-828f-4b78-bdea-3d876cdbe61d" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_62cc75f0-0946-463e-a8bb-431dfb21396c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_62cc75f0-0946-463e-a8bb-431dfb21396c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_62cc75f0-0946-463e-a8bb-431dfb21396c" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_62cc75f0-0946-463e-a8bb-431dfb21396c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_6a7c6600-cd46-4cba-81b5-0fb2f38ef1ed" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_62cc75f0-0946-463e-a8bb-431dfb21396c" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_6a7c6600-cd46-4cba-81b5-0fb2f38ef1ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_ea1f523f-3e0d-4384-aaa3-a7b9c2bda1cc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_6a7c6600-cd46-4cba-81b5-0fb2f38ef1ed" xlink:to="loc_us-gaap_CostOfSalesMember_ea1f523f-3e0d-4384-aaa3-a7b9c2bda1cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_c2cc8e2e-d026-421e-9c4b-df4ddad0aac3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_6a7c6600-cd46-4cba-81b5-0fb2f38ef1ed" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_c2cc8e2e-d026-421e-9c4b-df4ddad0aac3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpenseMember_10596401-3a3a-480f-9493-92e942ca9c79" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SellingAndMarketingExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_6a7c6600-cd46-4cba-81b5-0fb2f38ef1ed" xlink:to="loc_us-gaap_SellingAndMarketingExpenseMember_10596401-3a3a-480f-9493-92e942ca9c79" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_3ac1dd9c-bc25-4a37-8c00-b2ed7da6043c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_6a7c6600-cd46-4cba-81b5-0fb2f38ef1ed" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_3ac1dd9c-bc25-4a37-8c00-b2ed7da6043c" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/NetIncomeLossPerShareScheduleofCalculationofBasicandDilutedNetIncomeLossPerShareDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#NetIncomeLossPerShareScheduleofCalculationofBasicandDilutedNetIncomeLossPerShareDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/NetIncomeLossPerShareScheduleofCalculationofBasicandDilutedNetIncomeLossPerShareDetails" xlink:type="extended" id="i0eb0b955a1e6436ea91505aa7e1219a5_NetIncomeLossPerShareScheduleofCalculationofBasicandDilutedNetIncomeLossPerShareDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasicLineItems_2260a078-efe5-447c-af02-a8f1208d5457" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareBasicLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasicAbstract_265b85ad-ccbc-42dc-a856-16e4f1293159" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_2260a078-efe5-447c-af02-a8f1208d5457" xlink:to="loc_us-gaap_EarningsPerShareBasicAbstract_265b85ad-ccbc-42dc-a856-16e4f1293159" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_2cf2b497-65c6-4d05-883b-887faad01eca" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_265b85ad-ccbc-42dc-a856-16e4f1293159" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_2cf2b497-65c6-4d05-883b-887faad01eca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_39b28fee-c981-4792-9635-d890e17debc4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_265b85ad-ccbc-42dc-a856-16e4f1293159" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_39b28fee-c981-4792-9635-d890e17debc4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_845ad1ad-8031-4e56-98a7-91a4dced9d4f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_265b85ad-ccbc-42dc-a856-16e4f1293159" xlink:to="loc_us-gaap_EarningsPerShareBasic_845ad1ad-8031-4e56-98a7-91a4dced9d4f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDilutedAbstract_b59866d6-b77e-49ed-8e4a-2bcb1a8dc3cf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareDilutedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_2260a078-efe5-447c-af02-a8f1208d5457" xlink:to="loc_us-gaap_EarningsPerShareDilutedAbstract_b59866d6-b77e-49ed-8e4a-2bcb1a8dc3cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_a993412d-39f7-4427-aa2a-654297df999f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_b59866d6-b77e-49ed-8e4a-2bcb1a8dc3cf" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_a993412d-39f7-4427-aa2a-654297df999f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_ReallocationOfUndistributedIncomeLossResultOfConversionOfCommonStock_c705c780-09ba-4885-b19c-946583168cbc" xlink:href="ddog-20220331.xsd#ddog_ReallocationOfUndistributedIncomeLossResultOfConversionOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_b59866d6-b77e-49ed-8e4a-2bcb1a8dc3cf" xlink:to="loc_ddog_ReallocationOfUndistributedIncomeLossResultOfConversionOfCommonStock_c705c780-09ba-4885-b19c-946583168cbc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UndistributedEarningsLossAvailableToCommonShareholdersDiluted_7bb2c940-c1b5-4649-add6-535315e5d09d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_UndistributedEarningsLossAvailableToCommonShareholdersDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_b59866d6-b77e-49ed-8e4a-2bcb1a8dc3cf" xlink:to="loc_us-gaap_UndistributedEarningsLossAvailableToCommonShareholdersDiluted_7bb2c940-c1b5-4649-add6-535315e5d09d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_68ebb19a-3a26-4841-a22e-8c5983b33bd1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_5177ea9a-3bde-490e-951c-6bf89e44f549" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_2260a078-efe5-447c-af02-a8f1208d5457" xlink:to="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_5177ea9a-3bde-490e-951c-6bf89e44f549" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_WeightedAverageNumberDilutedSharesOutstandingConversionOfCommonSharesClass_1517a661-71f3-4790-aad7-83f1333d5f72" xlink:href="ddog-20220331.xsd#ddog_WeightedAverageNumberDilutedSharesOutstandingConversionOfCommonSharesClass"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_5177ea9a-3bde-490e-951c-6bf89e44f549" xlink:to="loc_ddog_WeightedAverageNumberDilutedSharesOutstandingConversionOfCommonSharesClass_1517a661-71f3-4790-aad7-83f1333d5f72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_75e18783-4379-48d5-94fc-0412fdc9e37a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_5177ea9a-3bde-490e-951c-6bf89e44f549" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_75e18783-4379-48d5-94fc-0412fdc9e37a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities_c44b7656-6be5-473d-8db0-d86fb5c060e5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_5177ea9a-3bde-490e-951c-6bf89e44f549" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities_c44b7656-6be5-473d-8db0-d86fb5c060e5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_901fe3f3-fa0a-41ae-9495-b7f10734e247" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_2260a078-efe5-447c-af02-a8f1208d5457" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_901fe3f3-fa0a-41ae-9495-b7f10734e247" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_74b05a53-2a25-4eaa-977f-391722ebd239" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_2260a078-efe5-447c-af02-a8f1208d5457" xlink:to="loc_us-gaap_EarningsPerShareDiluted_74b05a53-2a25-4eaa-977f-391722ebd239" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_b5c31245-3804-45a8-8af7-95c923c15246" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_2260a078-efe5-447c-af02-a8f1208d5457" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_b5c31245-3804-45a8-8af7-95c923c15246" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_f590d73b-a462-4ed1-bae5-26140cc37bc2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_b5c31245-3804-45a8-8af7-95c923c15246" xlink:to="loc_us-gaap_StatementClassOfStockAxis_f590d73b-a462-4ed1-bae5-26140cc37bc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_f590d73b-a462-4ed1-bae5-26140cc37bc2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f590d73b-a462-4ed1-bae5-26140cc37bc2" xlink:to="loc_us-gaap_ClassOfStockDomain_f590d73b-a462-4ed1-bae5-26140cc37bc2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_5b1bcec2-fe07-45ac-b112-97896efaae38" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f590d73b-a462-4ed1-bae5-26140cc37bc2" xlink:to="loc_us-gaap_ClassOfStockDomain_5b1bcec2-fe07-45ac-b112-97896efaae38" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_99be69f8-b66e-4573-beea-c7efa59d2e0e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_5b1bcec2-fe07-45ac-b112-97896efaae38" xlink:to="loc_us-gaap_CommonClassAMember_99be69f8-b66e-4573-beea-c7efa59d2e0e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_df340afd-f7a2-46c7-8712-f7dbb7091180" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_5b1bcec2-fe07-45ac-b112-97896efaae38" xlink:to="loc_us-gaap_CommonClassBMember_df340afd-f7a2-46c7-8712-f7dbb7091180" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_02c938ac-03a3-4543-ad4a-8dbc3fed8bb1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_b5c31245-3804-45a8-8af7-95c923c15246" xlink:to="loc_us-gaap_AwardTypeAxis_02c938ac-03a3-4543-ad4a-8dbc3fed8bb1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_02c938ac-03a3-4543-ad4a-8dbc3fed8bb1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_02c938ac-03a3-4543-ad4a-8dbc3fed8bb1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_02c938ac-03a3-4543-ad4a-8dbc3fed8bb1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_da4e6f02-802d-4dea-b422-a47e84b50c15" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_02c938ac-03a3-4543-ad4a-8dbc3fed8bb1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_da4e6f02-802d-4dea-b422-a47e84b50c15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_c36aa363-283d-4628-8717-c4445424647d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_da4e6f02-802d-4dea-b422-a47e84b50c15" xlink:to="loc_us-gaap_EmployeeStockOptionMember_c36aa363-283d-4628-8717-c4445424647d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_UnvestedEarlyExercisesAwardsMember_34c64de9-c107-425b-83cd-ee463ce21da6" xlink:href="ddog-20220331.xsd#ddog_UnvestedEarlyExercisesAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_da4e6f02-802d-4dea-b422-a47e84b50c15" xlink:to="loc_ddog_UnvestedEarlyExercisesAwardsMember_34c64de9-c107-425b-83cd-ee463ce21da6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_3504851b-fcd6-4ab6-bf8a-c0b9842abb96" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_da4e6f02-802d-4dea-b422-a47e84b50c15" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_3504851b-fcd6-4ab6-bf8a-c0b9842abb96" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_b3cead9c-7256-4a3b-9d2b-484ce5e50139" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_da4e6f02-802d-4dea-b422-a47e84b50c15" xlink:to="loc_us-gaap_RestrictedStockMember_b3cead9c-7256-4a3b-9d2b-484ce5e50139" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.datadoghq.com/role/NetIncomeLossPerShareScheduleofPotentiallyDilutiveSecuritiesnotIncludedinDilutedPerShareCalculationsDetails" xlink:type="simple" xlink:href="ddog-20220331.xsd#NetIncomeLossPerShareScheduleofPotentiallyDilutiveSecuritiesnotIncludedinDilutedPerShareCalculationsDetails"/>
  <link:definitionLink xlink:role="http://www.datadoghq.com/role/NetIncomeLossPerShareScheduleofPotentiallyDilutiveSecuritiesnotIncludedinDilutedPerShareCalculationsDetails" xlink:type="extended" id="i9e0386d09b58469aaa96dc7c3711ebd7_NetIncomeLossPerShareScheduleofPotentiallyDilutiveSecuritiesnotIncludedinDilutedPerShareCalculationsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_bcccbc96-738d-4439-97eb-fd9f65ecfdbf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_761a3db4-187f-4ffb-9d23-85fa085cb954" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_bcccbc96-738d-4439-97eb-fd9f65ecfdbf" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_761a3db4-187f-4ffb-9d23-85fa085cb954" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_cbf0620a-81fb-49a2-8423-ad9357b50b83" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_bcccbc96-738d-4439-97eb-fd9f65ecfdbf" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_cbf0620a-81fb-49a2-8423-ad9357b50b83" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3f8c844f-9398-4d22-b8c7-7e530bdcea33" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_cbf0620a-81fb-49a2-8423-ad9357b50b83" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3f8c844f-9398-4d22-b8c7-7e530bdcea33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_3f8c844f-9398-4d22-b8c7-7e530bdcea33_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3f8c844f-9398-4d22-b8c7-7e530bdcea33" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_3f8c844f-9398-4d22-b8c7-7e530bdcea33_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_aa8d0e2e-cb84-4a03-b035-f75376c7c57d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3f8c844f-9398-4d22-b8c7-7e530bdcea33" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_aa8d0e2e-cb84-4a03-b035-f75376c7c57d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_EmployeeStockOptionAndRestrictedStockUnitMember_7889ef05-f7aa-424f-9b23-b869aa2cb475" xlink:href="ddog-20220331.xsd#ddog_EmployeeStockOptionAndRestrictedStockUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_aa8d0e2e-cb84-4a03-b035-f75376c7c57d" xlink:to="loc_ddog_EmployeeStockOptionAndRestrictedStockUnitMember_7889ef05-f7aa-424f-9b23-b869aa2cb475" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_UnvestedEarlyExercisedStockOptionsAndRestrictedStockMember_136aa0dd-67b0-4365-a725-878b8b55c6f9" xlink:href="ddog-20220331.xsd#ddog_UnvestedEarlyExercisedStockOptionsAndRestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_aa8d0e2e-cb84-4a03-b035-f75376c7c57d" xlink:to="loc_ddog_UnvestedEarlyExercisedStockOptionsAndRestrictedStockMember_136aa0dd-67b0-4365-a725-878b8b55c6f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_SharesSubjectToEmployeeStockPurchasePlanMember_5fcb4166-5dfb-4c79-b26b-40685effcc5c" xlink:href="ddog-20220331.xsd#ddog_SharesSubjectToEmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_aa8d0e2e-cb84-4a03-b035-f75376c7c57d" xlink:to="loc_ddog_SharesSubjectToEmployeeStockPurchasePlanMember_5fcb4166-5dfb-4c79-b26b-40685effcc5c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ddog_SharesIssuableUponConversionOfTheConvertibleSeniorNotesMember_07f92cd8-090e-4e7c-b236-f986ca3c042b" xlink:href="ddog-20220331.xsd#ddog_SharesIssuableUponConversionOfTheConvertibleSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_aa8d0e2e-cb84-4a03-b035-f75376c7c57d" xlink:to="loc_ddog_SharesIssuableUponConversionOfTheConvertibleSeniorNotesMember_07f92cd8-090e-4e7c-b236-f986ca3c042b" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-roles-2021-01-31.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfAdoptionMember" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TypeOfAdoptionMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountingStandardsUpdate202006Member" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountingStandardsUpdate202006Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember" xlink:to="loc_us-gaap_AccountingStandardsUpdate202006Member" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
