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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:01a15f0b-2dbf-7e45-9ea1-870c59f25336,g:22682173-1b26-4efd-9eb4-5ac1c647c676-->
<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.palantir.com/role/CoverPage" xlink:type="simple" xlink:href="pltr-20260930.xsd#CoverPage"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/CoverPage" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_01a15f0b-2ec3-7ce8-8f76-71968bcfa84f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_DocumentInformationTable_01a15f0b-2ec3-7ce8-8f76-71968bcfa84f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2ec3-7b87-b09a-870ff1322955" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_01a15f0b-2ec3-7ce8-8f76-71968bcfa84f" xlink:to="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2ec3-7b87-b09a-870ff1322955" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-7b87-b09a-870ff1322955_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2ec3-7b87-b09a-870ff1322955" xlink:to="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-7b87-b09a-870ff1322955_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-7b2e-ad30-96d62a37378f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2ec3-7b87-b09a-870ff1322955" xlink:to="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-7b2e-ad30-96d62a37378f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_01a15f0b-2ec3-7f46-ab5d-52e325f8c24f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-7b2e-ad30-96d62a37378f" xlink:to="loc_us-gaap_CommonClassAMember_01a15f0b-2ec3-7f46-ab5d-52e325f8c24f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_01a15f0b-2ec3-70a6-b2de-04a40ca72ef5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-7b2e-ad30-96d62a37378f" xlink:to="loc_us-gaap_CommonClassBMember_01a15f0b-2ec3-70a6-b2de-04a40ca72ef5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_CommonClassFMember_01a15f0b-2ec3-747b-b366-c4720d01df53" xlink:href="pltr-20260930.xsd#pltr_CommonClassFMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-7b2e-ad30-96d62a37378f" xlink:to="loc_pltr_CommonClassFMember_01a15f0b-2ec3-747b-b366-c4720d01df53" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_01a15f0b-2ec3-7a1d-9779-2b16127d23ef" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_DocumentType_01a15f0b-2ec3-7a1d-9779-2b16127d23ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_01a15f0b-2ec3-7d7c-8340-b592bf40b9d3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_DocumentQuarterlyReport_01a15f0b-2ec3-7d7c-8340-b592bf40b9d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_01a15f0b-2ec3-7df3-810e-677c494b7de9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_DocumentPeriodEndDate_01a15f0b-2ec3-7df3-810e-677c494b7de9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_01a15f0b-2ec3-7c72-bfeb-f176f11249ef" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_DocumentTransitionReport_01a15f0b-2ec3-7c72-bfeb-f176f11249ef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_01a15f0b-2ec3-70af-ae6d-0afd7ddc9e97" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityFileNumber_01a15f0b-2ec3-70af-ae6d-0afd7ddc9e97" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_01a15f0b-2ec3-7973-99d3-0e0c04807638" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityRegistrantName_01a15f0b-2ec3-7973-99d3-0e0c04807638" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_01a15f0b-2ec3-7bbb-9096-bf7d275dbd87" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityIncorporationStateCountryCode_01a15f0b-2ec3-7bbb-9096-bf7d275dbd87" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_01a15f0b-2ec3-7cd7-8d96-e80bf61b7eee" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityTaxIdentificationNumber_01a15f0b-2ec3-7cd7-8d96-e80bf61b7eee" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_01a15f0b-2ec3-7ff9-9dbb-7ea2fa1b8fc5" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityAddressAddressLine1_01a15f0b-2ec3-7ff9-9dbb-7ea2fa1b8fc5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_01a15f0b-2ec3-7dc2-8c00-48f160ba2f20" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityAddressCityOrTown_01a15f0b-2ec3-7dc2-8c00-48f160ba2f20" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_01a15f0b-2ec3-7b2a-a354-3c5a6768e975" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityAddressStateOrProvince_01a15f0b-2ec3-7b2a-a354-3c5a6768e975" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_01a15f0b-2ec3-7a3b-8a1c-fd878f379932" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityAddressPostalZipCode_01a15f0b-2ec3-7a3b-8a1c-fd878f379932" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_01a15f0b-2ec3-7c24-8006-5fea42f37860" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_CityAreaCode_01a15f0b-2ec3-7c24-8006-5fea42f37860" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_01a15f0b-2ec3-797e-9ef0-42b12f7c2e86" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_LocalPhoneNumber_01a15f0b-2ec3-797e-9ef0-42b12f7c2e86" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_01a15f0b-2ec3-7f9d-8ad3-07fcbe7f80fb" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_Security12bTitle_01a15f0b-2ec3-7f9d-8ad3-07fcbe7f80fb" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_01a15f0b-2ec3-7257-b7aa-d0d3cbf1c52a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_TradingSymbol_01a15f0b-2ec3-7257-b7aa-d0d3cbf1c52a" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_01a15f0b-2ec3-7423-ae42-29b1b735e20d" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_SecurityExchangeName_01a15f0b-2ec3-7423-ae42-29b1b735e20d" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_01a15f0b-2ec3-7ed7-8c39-9dc8758114af" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityCurrentReportingStatus_01a15f0b-2ec3-7ed7-8c39-9dc8758114af" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_01a15f0b-2ec3-7ddc-9d70-1bada9b3d731" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityInteractiveDataCurrent_01a15f0b-2ec3-7ddc-9d70-1bada9b3d731" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_01a15f0b-2ec3-7756-8910-185d822a3457" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityFilerCategory_01a15f0b-2ec3-7756-8910-185d822a3457" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_01a15f0b-2ec3-7b3e-872f-2ae2d3a886f0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntitySmallBusiness_01a15f0b-2ec3-7b3e-872f-2ae2d3a886f0" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_01a15f0b-2ec3-71cf-9c17-54e309f53fb1" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityEmergingGrowthCompany_01a15f0b-2ec3-71cf-9c17-54e309f53fb1" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_01a15f0b-2ec3-70ac-be13-57194a055524" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityShellCompany_01a15f0b-2ec3-70ac-be13-57194a055524" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_01a15f0b-2ec3-737d-8690-3cc7ab9bc7bf" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_01a15f0b-2ec3-737d-8690-3cc7ab9bc7bf" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_01a15f0b-2ec3-7d74-b3f3-602c10df8a4e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_EntityCentralIndexKey_01a15f0b-2ec3-7d74-b3f3-602c10df8a4e" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_01a15f0b-2ec3-7e80-831c-ae2cfe986e81" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_AmendmentFlag_01a15f0b-2ec3-7e80-831c-ae2cfe986e81" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_01a15f0b-2ec3-7e7d-9589-04a686bfc558" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_DocumentFiscalPeriodFocus_01a15f0b-2ec3-7e7d-9589-04a686bfc558" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_01a15f0b-2ec3-7ff8-8516-bd78b2a9a30f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_DocumentFiscalYearFocus_01a15f0b-2ec3-7ff8-8516-bd78b2a9a30f" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_01a15f0b-2ec3-7596-9ec3-4297c4dd018e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a15f0b-2ec3-7ae8-bee2-b0ff8a295daf" xlink:to="loc_dei_CurrentFiscalYearEndDate_01a15f0b-2ec3-7596-9ec3-4297c4dd018e" xlink:type="arc" order="28"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/CondensedConsolidatedBalanceSheetsParenthetical" xlink:type="simple" xlink:href="pltr-20260930.xsd#CondensedConsolidatedBalanceSheetsParenthetical"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/CondensedConsolidatedBalanceSheetsParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_01a15f0b-2ec3-779c-8b2d-93953df817dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_01a15f0b-2ec3-773b-a8b1-54b7b0a270dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_01a15f0b-2ec3-779c-8b2d-93953df817dc" xlink:to="loc_us-gaap_StatementTable_01a15f0b-2ec3-773b-a8b1-54b7b0a270dd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2ec3-7a9a-bd53-9250d12c0da9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_01a15f0b-2ec3-773b-a8b1-54b7b0a270dd" xlink:to="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2ec3-7a9a-bd53-9250d12c0da9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-7a9a-bd53-9250d12c0da9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2ec3-7a9a-bd53-9250d12c0da9" xlink:to="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-7a9a-bd53-9250d12c0da9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-71aa-b8be-45a41fc756c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2ec3-7a9a-bd53-9250d12c0da9" xlink:to="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-71aa-b8be-45a41fc756c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_01a15f0b-2ec3-7d0a-a38a-20db3a9319b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-71aa-b8be-45a41fc756c2" xlink:to="loc_us-gaap_CommonClassAMember_01a15f0b-2ec3-7d0a-a38a-20db3a9319b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_01a15f0b-2ec3-7b52-835e-6b8c4813b871" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-71aa-b8be-45a41fc756c2" xlink:to="loc_us-gaap_CommonClassBMember_01a15f0b-2ec3-7b52-835e-6b8c4813b871" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_CommonClassFMember_01a15f0b-2ec3-7fc4-a0b1-ee41bbd62414" xlink:href="pltr-20260930.xsd#pltr_CommonClassFMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a15f0b-2ec3-71aa-b8be-45a41fc756c2" xlink:to="loc_pltr_CommonClassFMember_01a15f0b-2ec3-7fc4-a0b1-ee41bbd62414" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_01a15f0b-2ec3-7855-8a37-91dd0a36fa68" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_01a15f0b-2ec3-779c-8b2d-93953df817dc" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_01a15f0b-2ec3-7855-8a37-91dd0a36fa68" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_01a15f0b-2ec3-7f44-9ff0-b4be84af2791" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_01a15f0b-2ec3-779c-8b2d-93953df817dc" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_01a15f0b-2ec3-7f44-9ff0-b4be84af2791" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_01a15f0b-2ec3-74a8-a566-088bc0bef6d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_01a15f0b-2ec3-779c-8b2d-93953df817dc" xlink:to="loc_us-gaap_CommonStockSharesIssued_01a15f0b-2ec3-74a8-a566-088bc0bef6d0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_01a15f0b-2ec3-798f-bc43-fefbf0e64293" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_01a15f0b-2ec3-779c-8b2d-93953df817dc" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_01a15f0b-2ec3-798f-bc43-fefbf0e64293" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/CondensedConsolidatedStatementsofEquity" xlink:type="simple" xlink:href="pltr-20260930.xsd#CondensedConsolidatedStatementsofEquity"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/CondensedConsolidatedStatementsofEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_01a15f0b-2ec3-7c06-b438-d62a781c6da4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_01a15f0b-2ec3-7df1-9d8c-d9e5955e0cdf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_01a15f0b-2ec3-7c06-b438-d62a781c6da4" xlink:to="loc_us-gaap_StatementTable_01a15f0b-2ec3-7df1-9d8c-d9e5955e0cdf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_01a15f0b-2ec3-7c3a-949a-3a3fbc2a0758" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_01a15f0b-2ec3-7df1-9d8c-d9e5955e0cdf" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_01a15f0b-2ec3-7c3a-949a-3a3fbc2a0758" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_01a15f0b-2ec3-7c3a-949a-3a3fbc2a0758_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_01a15f0b-2ec3-7c3a-949a-3a3fbc2a0758" xlink:to="loc_us-gaap_EquityComponentDomain_01a15f0b-2ec3-7c3a-949a-3a3fbc2a0758_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_01a15f0b-2ec3-7cb4-ae60-cd2623466061" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_01a15f0b-2ec3-7c3a-949a-3a3fbc2a0758" xlink:to="loc_us-gaap_EquityComponentDomain_01a15f0b-2ec3-7cb4-ae60-cd2623466061" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ParentMember_01a15f0b-2ec3-70aa-878e-c9256cb016e5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a15f0b-2ec3-7cb4-ae60-cd2623466061" xlink:to="loc_us-gaap_ParentMember_01a15f0b-2ec3-70aa-878e-c9256cb016e5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_01a15f0b-2ec3-77ae-ae3d-383a05041f5c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParentMember_01a15f0b-2ec3-70aa-878e-c9256cb016e5" xlink:to="loc_us-gaap_CommonStockMember_01a15f0b-2ec3-77ae-ae3d-383a05041f5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_01a15f0b-2ec3-7ab7-b65f-6d1a55094857" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParentMember_01a15f0b-2ec3-70aa-878e-c9256cb016e5" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_01a15f0b-2ec3-7ab7-b65f-6d1a55094857" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_01a15f0b-2ec3-7926-899a-86f4a6f17825" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParentMember_01a15f0b-2ec3-70aa-878e-c9256cb016e5" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_01a15f0b-2ec3-7926-899a-86f4a6f17825" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_01a15f0b-2ec3-77d6-afd8-74a1b95aac1d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParentMember_01a15f0b-2ec3-70aa-878e-c9256cb016e5" xlink:to="loc_us-gaap_RetainedEarningsMember_01a15f0b-2ec3-77d6-afd8-74a1b95aac1d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_01a15f0b-2ec3-7f12-a02a-6b354367bd44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a15f0b-2ec3-7cb4-ae60-cd2623466061" xlink:to="loc_us-gaap_NoncontrollingInterestMember_01a15f0b-2ec3-7f12-a02a-6b354367bd44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_01a15f0b-2ec3-7c06-b438-d62a781c6da4" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_01a15f0b-2ec3-7eba-ba12-4387d9c69fce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_01a15f0b-2ec3-7eba-ba12-4387d9c69fce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_01a15f0b-2ec3-7578-bf06-884088812616" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_01a15f0b-2ec3-7578-bf06-884088812616" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_01a15f0b-2ec3-72bd-8d99-9ef8bebd347a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_01a15f0b-2ec3-72bd-8d99-9ef8bebd347a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_01a15f0b-2ec3-7355-8a67-bf60a6a75b6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_01a15f0b-2ec3-7355-8a67-bf60a6a75b6b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_01a164ce-28e2-7216-9f22-2f6614def75d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_01a164ce-28e2-7216-9f22-2f6614def75d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_01a1778e-5789-7398-978e-c28f8ff787d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_01a1778e-5789-7398-978e-c28f8ff787d2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_01a15f0b-2ec3-72ce-bc93-2b5863895114" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_01a15f0b-2ec3-72ce-bc93-2b5863895114" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_01a15f0b-2ec3-714f-a237-d0cd672409b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_01a15f0b-2ec3-714f-a237-d0cd672409b0" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_01a15f0b-2ec3-7a25-8ab2-53dfa3c339fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_01a15f0b-2ec3-7a25-8ab2-53dfa3c339fc" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_01a15f0b-2ec3-7417-bff5-33534df0b545" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_01a15f0b-2ec3-7417-bff5-33534df0b545" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_01a15f0b-2ec3-70bf-b091-321efaf59793" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_01a15f0b-2ec3-70bf-b091-321efaf59793" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_01a16a80-d231-7953-b943-239ec30f0ba9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_01a16a80-d231-7953-b943-239ec30f0ba9" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_01a15f0b-2ec3-7d44-8c5f-008de8343df7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01a15f0b-2ec3-7960-9ac1-2ad21d479e17" xlink:to="loc_us-gaap_ProfitLoss_01a15f0b-2ec3-7d44-8c5f-008de8343df7" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_01a15f0b-2ec3-7cdf-9205-b3b340dbc88b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_01a15f0b-2ec3-7e18-9f29-1a9703722cd1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/SignificantAccountingPoliciesDetails" xlink:type="simple" xlink:href="pltr-20260930.xsd#SignificantAccountingPoliciesDetails"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/SignificantAccountingPoliciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_01a15f0b-2f9a-7314-bf52-cfcc6b470035" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTable_01a15f0b-2f9a-7a81-bbf6-49cc7a04b221" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_01a15f0b-2f9a-7314-bf52-cfcc6b470035" xlink:to="loc_us-gaap_ConcentrationRiskTable_01a15f0b-2f9a-7a81-bbf6-49cc7a04b221" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_01a15f0b-2f9a-7044-bf88-f163beae9d8e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_01a15f0b-2f9a-7a81-bbf6-49cc7a04b221" xlink:to="loc_srt_MajorCustomersAxis_01a15f0b-2f9a-7044-bf88-f163beae9d8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_01a15f0b-2f9a-7044-bf88-f163beae9d8e_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_01a15f0b-2f9a-7044-bf88-f163beae9d8e" xlink:to="loc_srt_NameOfMajorCustomerDomain_01a15f0b-2f9a-7044-bf88-f163beae9d8e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_01a15f0b-2f9a-7d90-90b8-5b1e2009317e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_01a15f0b-2f9a-7044-bf88-f163beae9d8e" xlink:to="loc_srt_NameOfMajorCustomerDomain_01a15f0b-2f9a-7d90-90b8-5b1e2009317e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_CustomerIMember_01a15f0b-2f9a-7a48-baab-883e68c1c7ba" xlink:href="pltr-20260930.xsd#pltr_CustomerIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_01a15f0b-2f9a-7d90-90b8-5b1e2009317e" xlink:to="loc_pltr_CustomerIMember_01a15f0b-2f9a-7a48-baab-883e68c1c7ba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a15f0b-2f9a-7788-8269-f542810bac68" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_01a15f0b-2f9a-7a81-bbf6-49cc7a04b221" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a15f0b-2f9a-7788-8269-f542810bac68" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a15f0b-2f9a-7788-8269-f542810bac68_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a15f0b-2f9a-7788-8269-f542810bac68" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a15f0b-2f9a-7788-8269-f542810bac68_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a15f0b-2f9a-76d5-acc5-03d671b3acb1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a15f0b-2f9a-7788-8269-f542810bac68" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a15f0b-2f9a-76d5-acc5-03d671b3acb1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_AccountsReceivableBenchmarkMember_01a15f0b-2f9a-7c92-9454-7f4fa437b28e" xlink:href="pltr-20260930.xsd#pltr_AccountsReceivableBenchmarkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a15f0b-2f9a-76d5-acc5-03d671b3acb1" xlink:to="loc_pltr_AccountsReceivableBenchmarkMember_01a15f0b-2f9a-7c92-9454-7f4fa437b28e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_01a15f0b-2f9a-71e7-ace7-d1b9f9f70e62" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_01a15f0b-2f9a-7a81-bbf6-49cc7a04b221" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_01a15f0b-2f9a-71e7-ace7-d1b9f9f70e62" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_01a15f0b-2f9a-71e7-ace7-d1b9f9f70e62_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_01a15f0b-2f9a-71e7-ace7-d1b9f9f70e62" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_01a15f0b-2f9a-71e7-ace7-d1b9f9f70e62_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_01a15f0b-2f9a-7044-a114-d590ef3cfd2a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_01a15f0b-2f9a-71e7-ace7-d1b9f9f70e62" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_01a15f0b-2f9a-7044-a114-d590ef3cfd2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_01a15f0b-2f9a-7bbf-a468-4574ebef31a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_01a15f0b-2f9a-7044-a114-d590ef3cfd2a" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_01a15f0b-2f9a-7bbf-a468-4574ebef31a7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_01a15f0b-2f9a-7138-a3b5-04d88a3d1e98" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_01a15f0b-2f9a-7314-bf52-cfcc6b470035" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_01a15f0b-2f9a-7138-a3b5-04d88a3d1e98" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/ContractLiabilitiesandRemainingPerformanceObligationsAdditionalinformationDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#ContractLiabilitiesandRemainingPerformanceObligationsAdditionalinformationDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/ContractLiabilitiesandRemainingPerformanceObligationsAdditionalinformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_01a15f0b-2f9a-794f-8ffa-730b45409b19" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_01a15f0b-2f9a-794f-8ffa-730b45409b19" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_01a15f0b-2f9a-7e40-bb03-3b9a44b48d06" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_01a15f0b-2f9a-794f-8ffa-730b45409b19" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_01a15f0b-2f9a-7e40-bb03-3b9a44b48d06" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_01a15f0b-2f9a-76b0-a659-b7daf7ff2dac" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_01a15f0b-2f9a-794f-8ffa-730b45409b19" xlink:to="loc_srt_RangeAxis_01a15f0b-2f9a-76b0-a659-b7daf7ff2dac" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a15f0b-2f9a-76b0-a659-b7daf7ff2dac_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_01a15f0b-2f9a-76b0-a659-b7daf7ff2dac" xlink:to="loc_srt_RangeMember_01a15f0b-2f9a-76b0-a659-b7daf7ff2dac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a15f0b-2f9a-7bda-a778-fda791ac047a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_01a15f0b-2f9a-76b0-a659-b7daf7ff2dac" xlink:to="loc_srt_RangeMember_01a15f0b-2f9a-7bda-a778-fda791ac047a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_01a15f0b-2f9a-766c-a452-4f01e255b9f9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a15f0b-2f9a-7bda-a778-fda791ac047a" xlink:to="loc_srt_MinimumMember_01a15f0b-2f9a-766c-a452-4f01e255b9f9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_01a15f0b-2f9a-79f7-9907-19e2cc00e418" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a15f0b-2f9a-7bda-a778-fda791ac047a" xlink:to="loc_srt_MaximumMember_01a15f0b-2f9a-79f7-9907-19e2cc00e418" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_01a15f0b-2f9a-702e-8e97-ba6d28f9cd25" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:to="loc_us-gaap_ContractWithCustomerLiability_01a15f0b-2f9a-702e-8e97-ba6d28f9cd25" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_01a15f0b-2f9a-717f-9aa8-083365e08dd4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_01a15f0b-2f9a-717f-9aa8-083365e08dd4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_01a15f0b-2f9a-7522-b687-38eec2a35dc7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_01a15f0b-2f9a-7522-b687-38eec2a35dc7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_01a15f0b-2f9a-7fa1-82d1-62523ec1d77b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_01a15f0b-2f9a-7fa1-82d1-62523ec1d77b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_01a15f0b-2f9a-765c-acc0-b44aad9b9c4f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_01a15f0b-2f9a-765c-acc0-b44aad9b9c4f" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/ContractLiabilitiesandRemainingPerformanceObligationsAdditionalinformationDetail_1" xlink:type="simple" xlink:href="pltr-20260930.xsd#ContractLiabilitiesandRemainingPerformanceObligationsAdditionalinformationDetail_1"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/ContractLiabilitiesandRemainingPerformanceObligationsAdditionalinformationDetail_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_01a15f0b-2f9a-794f-8ffa-730b45409b19" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_01a15f0b-2f9a-794f-8ffa-730b45409b19" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_01a15f0b-2f9a-76b0-a659-b7daf7ff2dac" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_01a15f0b-2f9a-794f-8ffa-730b45409b19" xlink:to="loc_srt_RangeAxis_01a15f0b-2f9a-76b0-a659-b7daf7ff2dac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a15f0b-2f9a-76b0-a659-b7daf7ff2dac_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_01a15f0b-2f9a-76b0-a659-b7daf7ff2dac" xlink:to="loc_srt_RangeMember_01a15f0b-2f9a-76b0-a659-b7daf7ff2dac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a15f0b-2f9a-7bda-a778-fda791ac047a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_01a15f0b-2f9a-76b0-a659-b7daf7ff2dac" xlink:to="loc_srt_RangeMember_01a15f0b-2f9a-7bda-a778-fda791ac047a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_01a15f0b-2f9a-766c-a452-4f01e255b9f9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a15f0b-2f9a-7bda-a778-fda791ac047a" xlink:to="loc_srt_MinimumMember_01a15f0b-2f9a-766c-a452-4f01e255b9f9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_01a15f0b-2f9a-79f7-9907-19e2cc00e418" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a15f0b-2f9a-7bda-a778-fda791ac047a" xlink:to="loc_srt_MaximumMember_01a15f0b-2f9a-79f7-9907-19e2cc00e418" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_01a15f0b-2f9a-702e-8e97-ba6d28f9cd25" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:to="loc_us-gaap_ContractWithCustomerLiability_01a15f0b-2f9a-702e-8e97-ba6d28f9cd25" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_01a15f0b-2f9a-717f-9aa8-083365e08dd4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_01a15f0b-2f9a-717f-9aa8-083365e08dd4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_01a15f0b-2f9a-7522-b687-38eec2a35dc7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_01a15f0b-2f9a-7522-b687-38eec2a35dc7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_01a15f0b-2f9a-7fa1-82d1-62523ec1d77b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_01a15f0b-2f9a-7fa1-82d1-62523ec1d77b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_01a15f0b-2f9a-765c-acc0-b44aad9b9c4f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01a15f0b-2f9a-77c7-a8c8-14d3bbcf0146" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_01a15f0b-2f9a-765c-acc0-b44aad9b9c4f" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/InvestmentsandFairValueMeasurementsSummaryOfAssetsAndLiabilitiesThatAreMeasuredAtFairValueOnARecurringAndNonrecurringBasisDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#InvestmentsandFairValueMeasurementsSummaryOfAssetsAndLiabilitiesThatAreMeasuredAtFairValueOnARecurringAndNonrecurringBasisDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/InvestmentsandFairValueMeasurementsSummaryOfAssetsAndLiabilitiesThatAreMeasuredAtFairValueOnARecurringAndNonrecurringBasisDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a15f0b-2f9a-7f9b-be7e-b377e074e972" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a15f0b-2f9a-7eca-acd7-d5a5d89a80cf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a15f0b-2f9a-7f9b-be7e-b377e074e972" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a15f0b-2f9a-7eca-acd7-d5a5d89a80cf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfFinancialPositionLocationBalanceAxis_01a15f0b-2f9a-7356-8eb3-c8940b458466" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementOfFinancialPositionLocationBalanceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a15f0b-2f9a-7eca-acd7-d5a5d89a80cf" xlink:to="loc_us-gaap_StatementOfFinancialPositionLocationBalanceAxis_01a15f0b-2f9a-7356-8eb3-c8940b458466" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_01a15f0b-2f9a-779d-a8ea-55837e243dd4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a15f0b-2f9a-7eca-acd7-d5a5d89a80cf" xlink:to="loc_us-gaap_FinancialInstrumentAxis_01a15f0b-2f9a-779d-a8ea-55837e243dd4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-779d-a8ea-55837e243dd4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a15f0b-2f9a-779d-a8ea-55837e243dd4" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-779d-a8ea-55837e243dd4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7a5c-ac86-057e8cc20277" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a15f0b-2f9a-779d-a8ea-55837e243dd4" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7a5c-ac86-057e8cc20277" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_01a15f0b-2f9a-7906-80c0-a8bf12d9e221" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7a5c-ac86-057e8cc20277" xlink:to="loc_us-gaap_MoneyMarketFundsMember_01a15f0b-2f9a-7906-80c0-a8bf12d9e221" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_01a15f0b-2f9a-7d71-aa76-ed937a8f6360" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7a5c-ac86-057e8cc20277" xlink:to="loc_us-gaap_CertificatesOfDepositMember_01a15f0b-2f9a-7d71-aa76-ed937a8f6360" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_01a15f0b-2f9a-7129-a1ed-a339fceefdb7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7a5c-ac86-057e8cc20277" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_01a15f0b-2f9a-7129-a1ed-a339fceefdb7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesMember_01a15f0b-2f9a-7a2e-82fc-9342b5b71d5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7a5c-ac86-057e8cc20277" xlink:to="loc_us-gaap_EquitySecuritiesMember_01a15f0b-2f9a-7a2e-82fc-9342b5b71d5b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a15f0b-2f9a-7877-8769-93bc39e410bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a15f0b-2f9a-7eca-acd7-d5a5d89a80cf" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a15f0b-2f9a-7877-8769-93bc39e410bd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7877-8769-93bc39e410bd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a15f0b-2f9a-7877-8769-93bc39e410bd" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7877-8769-93bc39e410bd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7d6c-802a-6efb03bc15d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a15f0b-2f9a-7877-8769-93bc39e410bd" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7d6c-802a-6efb03bc15d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_01a15f0b-2f9a-7af6-bcdf-75e8aeb7cc3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7d6c-802a-6efb03bc15d6" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_01a15f0b-2f9a-7af6-bcdf-75e8aeb7cc3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_01a15f0b-2f9a-79e1-a8d5-a54885e2140b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7d6c-802a-6efb03bc15d6" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_01a15f0b-2f9a-79e1-a8d5-a54885e2140b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_01a15f0b-2f9a-7014-b49a-31506ecfb3bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7d6c-802a-6efb03bc15d6" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_01a15f0b-2f9a-7014-b49a-31506ecfb3bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_01a15f0b-2f9a-70b7-9288-5b8dc7fddb87" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a15f0b-2f9a-7f9b-be7e-b377e074e972" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_01a15f0b-2f9a-70b7-9288-5b8dc7fddb87" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_01a15f0b-2f9a-7fa6-b300-9885cac03b2f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_01a15f0b-2f9a-70b7-9288-5b8dc7fddb87" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_01a15f0b-2f9a-7fa6-b300-9885cac03b2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAbstract_01a15f0b-2f9a-78e4-a5a2-01122f751b32" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a15f0b-2f9a-7f9b-be7e-b377e074e972" xlink:to="loc_us-gaap_RestrictedCashAbstract_01a15f0b-2f9a-78e4-a5a2-01122f751b32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsFairValueDisclosure_01a15f0b-2f9a-7520-9470-32534267d22d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAbstract_01a15f0b-2f9a-78e4-a5a2-01122f751b32" xlink:to="loc_us-gaap_OtherAssetsFairValueDisclosure_01a15f0b-2f9a-7520-9470-32534267d22d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesAbstract_01a15f0b-2f9a-70f1-9564-90e6febb88b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a15f0b-2f9a-7f9b-be7e-b377e074e972" xlink:to="loc_us-gaap_MarketableSecuritiesAbstract_01a15f0b-2f9a-70f1-9564-90e6febb88b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_01a15f0b-2f9a-7a94-9476-d383a23befaa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesAbstract_01a15f0b-2f9a-70f1-9564-90e6febb88b7" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_01a15f0b-2f9a-7a94-9476-d383a23befaa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNi_01a15f0b-2f9a-758d-8e72-f8bb2e6f473d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesFvNi"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesAbstract_01a15f0b-2f9a-70f1-9564-90e6febb88b7" xlink:to="loc_us-gaap_EquitySecuritiesFvNi_01a15f0b-2f9a-758d-8e72-f8bb2e6f473d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_01a15f0b-2f9a-7653-b5a4-539135914503" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesAbstract_01a15f0b-2f9a-70f1-9564-90e6febb88b7" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_01a15f0b-2f9a-7653-b5a4-539135914503" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/InvestmentsandFairValueMeasurementsSummaryOfAssetsAndLiabilitiesThatAreMeasuredAtFairValueOnARecurringAndNonrecurringBasisDetail_1" xlink:type="simple" xlink:href="pltr-20260930.xsd#InvestmentsandFairValueMeasurementsSummaryOfAssetsAndLiabilitiesThatAreMeasuredAtFairValueOnARecurringAndNonrecurringBasisDetail_1"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/InvestmentsandFairValueMeasurementsSummaryOfAssetsAndLiabilitiesThatAreMeasuredAtFairValueOnARecurringAndNonrecurringBasisDetail_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a15f0b-2f9a-7f9b-be7e-b377e074e972" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a15f0b-2f9a-7eca-acd7-d5a5d89a80cf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a15f0b-2f9a-7f9b-be7e-b377e074e972" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a15f0b-2f9a-7eca-acd7-d5a5d89a80cf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_01a15f0b-2f9a-779d-a8ea-55837e243dd4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a15f0b-2f9a-7eca-acd7-d5a5d89a80cf" xlink:to="loc_us-gaap_FinancialInstrumentAxis_01a15f0b-2f9a-779d-a8ea-55837e243dd4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-779d-a8ea-55837e243dd4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a15f0b-2f9a-779d-a8ea-55837e243dd4" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-779d-a8ea-55837e243dd4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7a5c-ac86-057e8cc20277" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a15f0b-2f9a-779d-a8ea-55837e243dd4" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7a5c-ac86-057e8cc20277" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_01a15f0b-2f9a-7906-80c0-a8bf12d9e221" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7a5c-ac86-057e8cc20277" xlink:to="loc_us-gaap_MoneyMarketFundsMember_01a15f0b-2f9a-7906-80c0-a8bf12d9e221" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_01a15f0b-2f9a-7d71-aa76-ed937a8f6360" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7a5c-ac86-057e8cc20277" xlink:to="loc_us-gaap_CertificatesOfDepositMember_01a15f0b-2f9a-7d71-aa76-ed937a8f6360" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_01a15f0b-2f9a-7129-a1ed-a339fceefdb7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7a5c-ac86-057e8cc20277" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_01a15f0b-2f9a-7129-a1ed-a339fceefdb7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesMember_01a15f0b-2f9a-7a2e-82fc-9342b5b71d5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7a5c-ac86-057e8cc20277" xlink:to="loc_us-gaap_EquitySecuritiesMember_01a15f0b-2f9a-7a2e-82fc-9342b5b71d5b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a15f0b-2f9a-7877-8769-93bc39e410bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a15f0b-2f9a-7eca-acd7-d5a5d89a80cf" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a15f0b-2f9a-7877-8769-93bc39e410bd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7877-8769-93bc39e410bd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a15f0b-2f9a-7877-8769-93bc39e410bd" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7877-8769-93bc39e410bd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7d6c-802a-6efb03bc15d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_01a15f0b-2f9a-7877-8769-93bc39e410bd" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7d6c-802a-6efb03bc15d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_01a15f0b-2f9a-7af6-bcdf-75e8aeb7cc3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7d6c-802a-6efb03bc15d6" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_01a15f0b-2f9a-7af6-bcdf-75e8aeb7cc3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_01a15f0b-2f9a-79e1-a8d5-a54885e2140b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7d6c-802a-6efb03bc15d6" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_01a15f0b-2f9a-79e1-a8d5-a54885e2140b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_01a15f0b-2f9a-7014-b49a-31506ecfb3bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_01a15f0b-2f9a-7d6c-802a-6efb03bc15d6" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_01a15f0b-2f9a-7014-b49a-31506ecfb3bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_01a15f0b-2f9a-70b7-9288-5b8dc7fddb87" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a15f0b-2f9a-7f9b-be7e-b377e074e972" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_01a15f0b-2f9a-70b7-9288-5b8dc7fddb87" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_01a15f0b-2f9a-7fa6-b300-9885cac03b2f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValueAbstract_01a15f0b-2f9a-70b7-9288-5b8dc7fddb87" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_01a15f0b-2f9a-7fa6-b300-9885cac03b2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAbstract_01a15f0b-2f9a-78e4-a5a2-01122f751b32" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a15f0b-2f9a-7f9b-be7e-b377e074e972" xlink:to="loc_us-gaap_RestrictedCashAbstract_01a15f0b-2f9a-78e4-a5a2-01122f751b32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsFairValueDisclosure_01a15f0b-2f9a-7520-9470-32534267d22d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAbstract_01a15f0b-2f9a-78e4-a5a2-01122f751b32" xlink:to="loc_us-gaap_OtherAssetsFairValueDisclosure_01a15f0b-2f9a-7520-9470-32534267d22d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecuritiesAbstract_01a15f0b-2f9a-70f1-9564-90e6febb88b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecuritiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a15f0b-2f9a-7f9b-be7e-b377e074e972" xlink:to="loc_us-gaap_MarketableSecuritiesAbstract_01a15f0b-2f9a-70f1-9564-90e6febb88b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_01a15f0b-2f9a-7a94-9476-d383a23befaa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesAbstract_01a15f0b-2f9a-70f1-9564-90e6febb88b7" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_01a15f0b-2f9a-7a94-9476-d383a23befaa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNi_01a15f0b-2f9a-758d-8e72-f8bb2e6f473d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesFvNi"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesAbstract_01a15f0b-2f9a-70f1-9564-90e6febb88b7" xlink:to="loc_us-gaap_EquitySecuritiesFvNi_01a15f0b-2f9a-758d-8e72-f8bb2e6f473d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_01a15f0b-2f9a-7653-b5a4-539135914503" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesAbstract_01a15f0b-2f9a-70f1-9564-90e6febb88b7" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_01a15f0b-2f9a-7653-b5a4-539135914503" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/InvestmentsandFairValueMeasurementsAvailableForSaleDebtSecuritiesDetails" xlink:type="simple" xlink:href="pltr-20260930.xsd#InvestmentsandFairValueMeasurementsAvailableForSaleDebtSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/InvestmentsandFairValueMeasurementsAvailableForSaleDebtSecuritiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_01a15f0b-2f9a-7e95-a32d-9b9f6b359955" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_01a15f0b-2f9a-74c0-9398-3e7f13fdd846" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_01a15f0b-2f9a-7e95-a32d-9b9f6b359955" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_01a15f0b-2f9a-74c0-9398-3e7f13fdd846" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_01a15f0b-2f9a-7c14-8776-9eb2e93a7428" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_01a15f0b-2f9a-74c0-9398-3e7f13fdd846" xlink:to="loc_us-gaap_FinancialInstrumentAxis_01a15f0b-2f9a-7c14-8776-9eb2e93a7428" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7c14-8776-9eb2e93a7428_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a15f0b-2f9a-7c14-8776-9eb2e93a7428" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7c14-8776-9eb2e93a7428_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7f8f-8677-d8f61431b4b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a15f0b-2f9a-7c14-8776-9eb2e93a7428" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7f8f-8677-d8f61431b4b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_01a15f0b-2f9a-760d-80d0-e73bc849bf6f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a15f0b-2f9a-7f8f-8677-d8f61431b4b9" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_01a15f0b-2f9a-760d-80d0-e73bc849bf6f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_01a15f0b-2f9a-7e6a-818a-f92e653b348a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_01a15f0b-2f9a-7e95-a32d-9b9f6b359955" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_01a15f0b-2f9a-7e6a-818a-f92e653b348a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_01a15f0b-2f9a-7af9-9819-7bd55c3aed04" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_01a15f0b-2f9a-7e95-a32d-9b9f6b359955" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_01a15f0b-2f9a-7af9-9819-7bd55c3aed04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_01a15f0b-2f9a-742f-bd76-bdeb7122892a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_01a15f0b-2f9a-7e95-a32d-9b9f6b359955" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_01a15f0b-2f9a-742f-bd76-bdeb7122892a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_01a15f0b-2f9a-7ba8-a936-4f5246c1e806" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_01a15f0b-2f9a-7e95-a32d-9b9f6b359955" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_01a15f0b-2f9a-7ba8-a936-4f5246c1e806" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/InvestmentsandFairValueMeasurementsAdditionalInformationDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#InvestmentsandFairValueMeasurementsAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/InvestmentsandFairValueMeasurementsAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a179d1-c9f9-7a24-bc41-1891ebf9a42e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a15f0b-2f9a-784b-a45e-e4fb0206cb8b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a179d1-c9f9-7a24-bc41-1891ebf9a42e" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a15f0b-2f9a-784b-a45e-e4fb0206cb8b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_01a179d7-0c05-764d-8937-3cadf269b9cc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_01a15f0b-2f9a-784b-a45e-e4fb0206cb8b" xlink:to="loc_us-gaap_FinancialInstrumentAxis_01a179d7-0c05-764d-8937-3cadf269b9cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a179d7-0c05-764d-8937-3cadf269b9cc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a179d7-0c05-764d-8937-3cadf269b9cc" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a179d7-0c05-764d-8937-3cadf269b9cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a179d7-0c05-7444-83bf-af08d45a7387" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01a179d7-0c05-764d-8937-3cadf269b9cc" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a179d7-0c05-7444-83bf-af08d45a7387" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_PubliclyTradedEquitySecuritiesHeldMember_01a179d7-0c05-7b16-869a-fbbbd8cc6fa6" xlink:href="pltr-20260930.xsd#pltr_PubliclyTradedEquitySecuritiesHeldMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01a179d7-0c05-7444-83bf-af08d45a7387" xlink:to="loc_pltr_PubliclyTradedEquitySecuritiesHeldMember_01a179d7-0c05-7b16-869a-fbbbd8cc6fa6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt_01a179d1-c9f9-73c1-84cb-33b328b613ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a179d1-c9f9-7a24-bc41-1891ebf9a42e" xlink:to="loc_us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt_01a179d1-c9f9-73c1-84cb-33b328b613ed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_01a179d6-6d55-7213-a8b6-d01418e41c1f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a179d1-c9f9-7a24-bc41-1891ebf9a42e" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_01a179d6-6d55-7213-a8b6-d01418e41c1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions_01a179d6-8e4f-709c-a426-dfe2d74a5edc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a179d1-c9f9-7a24-bc41-1891ebf9a42e" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions_01a179d6-8e4f-709c-a426-dfe2d74a5edc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiUnrealizedGainLoss_01a179d7-0c05-7d67-a15b-8166057ee8d5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesFvNiUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a179d1-c9f9-7a24-bc41-1891ebf9a42e" xlink:to="loc_us-gaap_EquitySecuritiesFvNiUnrealizedGainLoss_01a179d7-0c05-7d67-a15b-8166057ee8d5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_01a179d7-3e41-7ee8-9145-10f24b23afc4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_01a179d1-c9f9-7a24-bc41-1891ebf9a42e" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_01a179d7-3e41-7ee8-9145-10f24b23afc4" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/DebtDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#DebtDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/DebtDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtLineItems_01a15f0b-2f9a-7aa2-9d5f-27586c100d99" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermDebtLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShortTermDebtTable_01a15f0b-2f9a-7d71-a37d-9c75209ff8c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShortTermDebtTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShortTermDebtLineItems_01a15f0b-2f9a-7aa2-9d5f-27586c100d99" xlink:to="loc_us-gaap_ScheduleOfShortTermDebtTable_01a15f0b-2f9a-7d71-a37d-9c75209ff8c2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_01a15f0b-2f9a-771c-b2b8-07ecf3c0d3aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShortTermDebtTable_01a15f0b-2f9a-7d71-a37d-9c75209ff8c2" xlink:to="loc_us-gaap_CreditFacilityAxis_01a15f0b-2f9a-771c-b2b8-07ecf3c0d3aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_01a15f0b-2f9a-771c-b2b8-07ecf3c0d3aa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_01a15f0b-2f9a-771c-b2b8-07ecf3c0d3aa" xlink:to="loc_us-gaap_CreditFacilityDomain_01a15f0b-2f9a-771c-b2b8-07ecf3c0d3aa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_01a15f0b-2f9a-7ff2-8041-d51c9a0ac615" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_01a15f0b-2f9a-771c-b2b8-07ecf3c0d3aa" xlink:to="loc_us-gaap_CreditFacilityDomain_01a15f0b-2f9a-7ff2-8041-d51c9a0ac615" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_01a15f0b-2f9a-7578-abde-279da13e5a8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_01a15f0b-2f9a-7ff2-8041-d51c9a0ac615" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_01a15f0b-2f9a-7578-abde-279da13e5a8e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_01a15f0b-2f9a-7726-a940-7fff055d9f25" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShortTermDebtTable_01a15f0b-2f9a-7d71-a37d-9c75209ff8c2" xlink:to="loc_us-gaap_DebtInstrumentAxis_01a15f0b-2f9a-7726-a940-7fff055d9f25" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_01a15f0b-2f9a-7726-a940-7fff055d9f25_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_01a15f0b-2f9a-7726-a940-7fff055d9f25" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_01a15f0b-2f9a-7726-a940-7fff055d9f25_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_01a15f0b-2f9a-74a9-9871-70a8eafcc3b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_01a15f0b-2f9a-7726-a940-7fff055d9f25" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_01a15f0b-2f9a-74a9-9871-70a8eafcc3b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_TwoThousandAndFourteenRevolvingCreditFacilityMember_01a15f0b-2f9a-7128-b97b-ed7beb579b75" xlink:href="pltr-20260930.xsd#pltr_TwoThousandAndFourteenRevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_01a15f0b-2f9a-74a9-9871-70a8eafcc3b6" xlink:to="loc_pltr_TwoThousandAndFourteenRevolvingCreditFacilityMember_01a15f0b-2f9a-7128-b97b-ed7beb579b75" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_01a15f0b-2f9a-79d6-8c55-59248e7ccee1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShortTermDebtTable_01a15f0b-2f9a-7d71-a37d-9c75209ff8c2" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_01a15f0b-2f9a-79d6-8c55-59248e7ccee1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_01a15f0b-2f9a-79d6-8c55-59248e7ccee1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_01a15f0b-2f9a-79d6-8c55-59248e7ccee1" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_01a15f0b-2f9a-79d6-8c55-59248e7ccee1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_01a15f0b-2f9a-755a-a91f-e2151238fcd2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_01a15f0b-2f9a-79d6-8c55-59248e7ccee1" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_01a15f0b-2f9a-755a-a91f-e2151238fcd2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_01a15f0b-2f9a-7e9e-9c91-c2ce5312705e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_01a15f0b-2f9a-755a-a91f-e2151238fcd2" xlink:to="loc_us-gaap_LineOfCreditMember_01a15f0b-2f9a-7e9e-9c91-c2ce5312705e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_01a15f0b-2f9a-7c92-8a77-f8ceaf97011f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtLineItems_01a15f0b-2f9a-7aa2-9d5f-27586c100d99" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_01a15f0b-2f9a-7c92-8a77-f8ceaf97011f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_01a15f0b-2f9a-710f-9c82-a4c0d1524332" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtLineItems_01a15f0b-2f9a-7aa2-9d5f-27586c100d99" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_01a15f0b-2f9a-710f-9c82-a4c0d1524332" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_LineOfCreditMinimumLiquidityToBeMaintained_01a15f0b-2f9a-75d0-b1f3-ba44211aa14f" xlink:href="pltr-20260930.xsd#pltr_LineOfCreditMinimumLiquidityToBeMaintained"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtLineItems_01a15f0b-2f9a-7aa2-9d5f-27586c100d99" xlink:to="loc_pltr_LineOfCreditMinimumLiquidityToBeMaintained_01a15f0b-2f9a-75d0-b1f3-ba44211aa14f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/CommitmentsandContingenciesAdditionalInformationDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#CommitmentsandContingenciesAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/CommitmentsandContingenciesAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentLineItems_01a16568-2818-7663-9345-13585c4f4c38" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseCommitmentExcludingLongtermCommitmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentTable_01a16567-896e-7734-ac3f-61cb2f6831ac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseCommitmentExcludingLongtermCommitmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentLineItems_01a16568-2818-7663-9345-13585c4f4c38" xlink:to="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentTable_01a16567-896e-7734-ac3f-61cb2f6831ac" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis_01a16568-2818-7e3e-9f11-0a91f0f983f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentTable_01a16567-896e-7734-ac3f-61cb2f6831ac" xlink:to="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis_01a16568-2818-7e3e-9f11-0a91f0f983f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_01a16568-2818-7e3e-9f11-0a91f0f983f2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis_01a16568-2818-7e3e-9f11-0a91f0f983f2" xlink:to="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_01a16568-2818-7e3e-9f11-0a91f0f983f2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_01a16568-2818-7ebb-b1e6-0d094b5286fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis_01a16568-2818-7e3e-9f11-0a91f0f983f2" xlink:to="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_01a16568-2818-7ebb-b1e6-0d094b5286fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseCommitmentMember_01a16568-70ca-76ec-837e-c8e790ca9d82" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PurchaseCommitmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_01a16568-2818-7ebb-b1e6-0d094b5286fe" xlink:to="loc_us-gaap_PurchaseCommitmentMember_01a16568-70ca-76ec-837e-c8e790ca9d82" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_01a16569-716a-7c8b-987f-0835b79fc2db" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentTable_01a16567-896e-7734-ac3f-61cb2f6831ac" xlink:to="loc_srt_RangeAxis_01a16569-716a-7c8b-987f-0835b79fc2db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a16569-716a-7c8b-987f-0835b79fc2db_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_01a16569-716a-7c8b-987f-0835b79fc2db" xlink:to="loc_srt_RangeMember_01a16569-716a-7c8b-987f-0835b79fc2db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a16569-c926-7a35-ad26-d6830efa0028" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_01a16569-716a-7c8b-987f-0835b79fc2db" xlink:to="loc_srt_RangeMember_01a16569-c926-7a35-ad26-d6830efa0028" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_01a1656a-d77b-7387-a9d8-1d64a9e0e47f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a16569-c926-7a35-ad26-d6830efa0028" xlink:to="loc_srt_MinimumMember_01a1656a-d77b-7387-a9d8-1d64a9e0e47f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_01a1656b-80f9-7395-9d9f-da28702b0195" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a16569-c926-7a35-ad26-d6830efa0028" xlink:to="loc_srt_MaximumMember_01a1656b-80f9-7395-9d9f-da28702b0195" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentAmount_01a16568-2818-7883-a116-0cce87db40bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermPurchaseCommitmentAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentLineItems_01a16568-2818-7663-9345-13585c4f4c38" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentAmount_01a16568-2818-7883-a116-0cce87db40bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermPurchaseCommitmentPeriod_01a1656c-7a0f-7beb-9a17-6d71b9dceb42" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermPurchaseCommitmentPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentLineItems_01a16568-2818-7663-9345-13585c4f4c38" xlink:to="loc_us-gaap_LongtermPurchaseCommitmentPeriod_01a1656c-7a0f-7beb-9a17-6d71b9dceb42" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/StockholdersEquityAdditionalInformationDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#StockholdersEquityAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/StockholdersEquityAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_01a15f0b-2f9a-76d0-a295-ff4c4516c417" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_01a15f0b-2f9a-76d3-ad9d-c22d2544dae1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a15f0b-2f9a-76d0-a295-ff4c4516c417" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_01a15f0b-2f9a-76d3-ad9d-c22d2544dae1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2f9a-77c7-b618-fb2e4d9b044a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_01a15f0b-2f9a-76d3-ad9d-c22d2544dae1" xlink:to="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2f9a-77c7-b618-fb2e4d9b044a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-77c7-b618-fb2e4d9b044a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2f9a-77c7-b618-fb2e4d9b044a" xlink:to="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-77c7-b618-fb2e4d9b044a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-786e-9cea-4eeb7270911d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2f9a-77c7-b618-fb2e4d9b044a" xlink:to="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-786e-9cea-4eeb7270911d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_01a15f0b-2f9a-795e-b611-8e03805179dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-786e-9cea-4eeb7270911d" xlink:to="loc_us-gaap_CommonClassAMember_01a15f0b-2f9a-795e-b611-8e03805179dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_01a15f0b-2f9a-7294-a3e5-eec539cb52f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-786e-9cea-4eeb7270911d" xlink:to="loc_us-gaap_CommonClassBMember_01a15f0b-2f9a-7294-a3e5-eec539cb52f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_CommonClassFMember_01a15f0b-2f9a-7711-9087-f9f2597a2cbd" xlink:href="pltr-20260930.xsd#pltr_CommonClassFMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-786e-9cea-4eeb7270911d" xlink:to="loc_pltr_CommonClassFMember_01a15f0b-2f9a-7711-9087-f9f2597a2cbd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_CommonStockVotingRightsNumberOfVotes_01a15f0b-2f9a-78b6-8e09-cdc724fc382b" xlink:href="pltr-20260930.xsd#pltr_CommonStockVotingRightsNumberOfVotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a15f0b-2f9a-76d0-a295-ff4c4516c417" xlink:to="loc_pltr_CommonStockVotingRightsNumberOfVotes_01a15f0b-2f9a-78b6-8e09-cdc724fc382b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_CommonStockConvertibleConversionRatio_01a15f0b-2f9a-7cf0-a884-4e6c06ed3e02" xlink:href="pltr-20260930.xsd#pltr_CommonStockConvertibleConversionRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a15f0b-2f9a-76d0-a295-ff4c4516c417" xlink:to="loc_pltr_CommonStockConvertibleConversionRatio_01a15f0b-2f9a-7cf0-a884-4e6c06ed3e02" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ControlOfTotalVotingPower_01a15f0b-2f9a-70ef-9d84-202ebbb73df6" xlink:href="pltr-20260930.xsd#pltr_ControlOfTotalVotingPower"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a15f0b-2f9a-76d0-a295-ff4c4516c417" xlink:to="loc_pltr_ControlOfTotalVotingPower_01a15f0b-2f9a-70ef-9d84-202ebbb73df6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_MinimumOwnershipThreshold_01a15f0b-2f9a-746b-ae13-aa4db05635f6" xlink:href="pltr-20260930.xsd#pltr_MinimumOwnershipThreshold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a15f0b-2f9a-76d0-a295-ff4c4516c417" xlink:to="loc_pltr_MinimumOwnershipThreshold_01a15f0b-2f9a-746b-ae13-aa4db05635f6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_01a15f0b-2f9a-7475-85f8-d4be049d4c70" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsPayableCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a15f0b-2f9a-76d0-a295-ff4c4516c417" xlink:to="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_01a15f0b-2f9a-7475-85f8-d4be049d4c70" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/StockholdersEquitySummaryofTotalAuthorizedIssuedAndOutstandingSharesDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#StockholdersEquitySummaryofTotalAuthorizedIssuedAndOutstandingSharesDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/StockholdersEquitySummaryofTotalAuthorizedIssuedAndOutstandingSharesDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_01a15f0b-2f9a-748a-82d2-3bd90a665735" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_01a15f0b-2f9a-7fde-ba2d-f266f15e7693" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a15f0b-2f9a-748a-82d2-3bd90a665735" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_01a15f0b-2f9a-7fde-ba2d-f266f15e7693" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2f9a-7933-b77c-570a4baa125d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_01a15f0b-2f9a-7fde-ba2d-f266f15e7693" xlink:to="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2f9a-7933-b77c-570a4baa125d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-7933-b77c-570a4baa125d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2f9a-7933-b77c-570a4baa125d" xlink:to="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-7933-b77c-570a4baa125d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-77a1-8650-a4fee749e67f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_01a15f0b-2f9a-7933-b77c-570a4baa125d" xlink:to="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-77a1-8650-a4fee749e67f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_01a15f0b-2f9a-7cd0-a1fb-12ea65182ebb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-77a1-8650-a4fee749e67f" xlink:to="loc_us-gaap_CommonClassAMember_01a15f0b-2f9a-7cd0-a1fb-12ea65182ebb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_01a15f0b-2f9a-7caa-b737-70557232dcd2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-77a1-8650-a4fee749e67f" xlink:to="loc_us-gaap_CommonClassBMember_01a15f0b-2f9a-7caa-b737-70557232dcd2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_CommonClassFMember_01a15f0b-2f9a-7e02-92ab-f78f3b778cec" xlink:href="pltr-20260930.xsd#pltr_CommonClassFMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_01a15f0b-2f9a-77a1-8650-a4fee749e67f" xlink:to="loc_pltr_CommonClassFMember_01a15f0b-2f9a-7e02-92ab-f78f3b778cec" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_01a15f0b-2f9a-7f82-9884-874b33d8d10a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a15f0b-2f9a-748a-82d2-3bd90a665735" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_01a15f0b-2f9a-7f82-9884-874b33d8d10a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_01a15f0b-2f9a-7cd4-88e2-cc1b45ed957b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a15f0b-2f9a-748a-82d2-3bd90a665735" xlink:to="loc_us-gaap_CommonStockSharesIssued_01a15f0b-2f9a-7cd4-88e2-cc1b45ed957b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_01a15f0b-2f9a-76f8-b241-96f508c50c19" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_01a15f0b-2f9a-748a-82d2-3bd90a665735" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_01a15f0b-2f9a-76f8-b241-96f508c50c19" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/StockBasedCompensationSummaryofSARsActivityDetails" xlink:type="simple" xlink:href="pltr-20260930.xsd#StockBasedCompensationSummaryofSARsActivityDetails"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/StockBasedCompensationSummaryofSARsActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7ba4-8158-7150c68272ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-7166-9b8c-090a1120e4ec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7ba4-8158-7150c68272ca" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-7166-9b8c-090a1120e4ec" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-7ed5-868b-27856932bd51" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-7166-9b8c-090a1120e4ec" xlink:to="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-7ed5-868b-27856932bd51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7ed5-868b-27856932bd51_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-7ed5-868b-27856932bd51" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7ed5-868b-27856932bd51_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7663-a309-bdf478428d39" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-7ed5-868b-27856932bd51" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7663-a309-bdf478428d39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockAppreciationRightsSARSMember_01a15f0b-2f9a-71d7-9904-5971d11313d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockAppreciationRightsSARSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7663-a309-bdf478428d39" xlink:to="loc_us-gaap_StockAppreciationRightsSARSMember_01a15f0b-2f9a-71d7-9904-5971d11313d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_01a15f0b-2f9a-77e1-93eb-ad8d9c1a2579" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7ba4-8158-7150c68272ca" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_01a15f0b-2f9a-77e1-93eb-ad8d9c1a2579" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_01a15f0b-2f9a-702e-853d-35f02f8602fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_01a15f0b-2f9a-77e1-93eb-ad8d9c1a2579" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_01a15f0b-2f9a-702e-853d-35f02f8602fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_01a15f0b-2f9a-74c2-9173-3d3dcbdc7330" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_01a15f0b-2f9a-77e1-93eb-ad8d9c1a2579" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_01a15f0b-2f9a-74c2-9173-3d3dcbdc7330" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercised_01a15f0b-2f9a-79c8-960c-a517ea46a755" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_01a15f0b-2f9a-77e1-93eb-ad8d9c1a2579" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercised_01a15f0b-2f9a-79c8-960c-a517ea46a755" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeituresAndExpirations_01a15f0b-2f9a-70f3-bb0e-3d646c5a2281" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeituresAndExpirations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_01a15f0b-2f9a-77e1-93eb-ad8d9c1a2579" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeituresAndExpirations_01a15f0b-2f9a-70f3-bb0e-3d646c5a2281" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_01a15f0b-2f9a-7cf7-8dd3-c2f80e42a9a5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsVestedAndExpectedToVestExercisableNumber_01a15f0b-2f9a-7688-ad19-08b68ad72ed9" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsVestedAndExpectedToVestExercisableNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7ba4-8158-7150c68272ca" xlink:to="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsVestedAndExpectedToVestExercisableNumber_01a15f0b-2f9a-7688-ad19-08b68ad72ed9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_01a15f0b-2f9a-78a4-bc01-fc17459fac22" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7ba4-8158-7150c68272ca" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_01a15f0b-2f9a-78a4-bc01-fc17459fac22" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice_01a15f0b-2f9a-77a2-b99e-053571be897c" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_01a15f0b-2f9a-78a4-bc01-fc17459fac22" xlink:to="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice_01a15f0b-2f9a-77a2-b99e-053571be897c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsInPeriodWeightedAverageExercisePrice_01a15f0b-2f9a-7cf3-990a-36722bc4193a" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_01a15f0b-2f9a-78a4-bc01-fc17459fac22" xlink:to="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsInPeriodWeightedAverageExercisePrice_01a15f0b-2f9a-7cf3-990a-36722bc4193a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisesInPeriodWeightedAverageExercisePrice_01a15f0b-2f9a-767a-8098-b191915732d3" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisesInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_01a15f0b-2f9a-78a4-bc01-fc17459fac22" xlink:to="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisesInPeriodWeightedAverageExercisePrice_01a15f0b-2f9a-767a-8098-b191915732d3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice_01a15f0b-2f9a-73c1-b748-95f21ed1622c" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_01a15f0b-2f9a-78a4-bc01-fc17459fac22" xlink:to="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice_01a15f0b-2f9a-73c1-b748-95f21ed1622c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice_01a15f0b-2f9a-75cd-a4ae-2ca9eb2cb473" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice_01a15f0b-2f9a-7196-9fe3-e23c5dadf158" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7ba4-8158-7150c68272ca" xlink:to="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice_01a15f0b-2f9a-7196-9fe3-e23c5dadf158" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_01a15f0b-2f9a-7806-9a2a-dc214992cf9b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7ba4-8158-7150c68272ca" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_01a15f0b-2f9a-7806-9a2a-dc214992cf9b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm_01a15f0b-2f9a-766e-a3d5-1e14765ea4e8" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7ba4-8158-7150c68272ca" xlink:to="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm_01a15f0b-2f9a-766e-a3d5-1e14765ea4e8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding_01a15f0b-2f9a-792d-98a3-135a8a74fe56" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7ba4-8158-7150c68272ca" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding_01a15f0b-2f9a-792d-98a3-135a8a74fe56" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsVestedAndExpectedToVestExercisableAggregateIntrinsicValue_01a15f0b-2f9a-78b0-a93e-4a1983347240" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsVestedAndExpectedToVestExercisableAggregateIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7ba4-8158-7150c68272ca" xlink:to="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsVestedAndExpectedToVestExercisableAggregateIntrinsicValue_01a15f0b-2f9a-78b0-a93e-4a1983347240" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/StockBasedCompensationAdditionalInformationDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#StockBasedCompensationAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/StockBasedCompensationAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-781b-be1d-6736a6569bc0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-76b4-b170-a0357550b0b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-781b-be1d-6736a6569bc0" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-76b4-b170-a0357550b0b4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-74ba-a5e4-a066ec391198" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-76b4-b170-a0357550b0b4" xlink:to="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-74ba-a5e4-a066ec391198" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-74ba-a5e4-a066ec391198_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-74ba-a5e4-a066ec391198" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-74ba-a5e4-a066ec391198_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7338-a8e6-4426cde1157c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-74ba-a5e4-a066ec391198" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7338-a8e6-4426cde1157c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_01a15f0b-2f9a-7045-98f1-5dbcaf4d1bf3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7338-a8e6-4426cde1157c" xlink:to="loc_us-gaap_EmployeeStockOptionMember_01a15f0b-2f9a-7045-98f1-5dbcaf4d1bf3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockAppreciationRightsSARSMember_01a15f0b-2f9a-7159-9ed3-e04ddd419302" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockAppreciationRightsSARSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7338-a8e6-4426cde1157c" xlink:to="loc_us-gaap_StockAppreciationRightsSARSMember_01a15f0b-2f9a-7159-9ed3-e04ddd419302" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_01a15f0b-2f9a-7971-a674-f63f4c257f81" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7338-a8e6-4426cde1157c" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_01a15f0b-2f9a-7971-a674-f63f4c257f81" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_01a15f0b-2f9a-7161-9c3f-58c36e2022e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7338-a8e6-4426cde1157c" xlink:to="loc_us-gaap_PerformanceSharesMember_01a15f0b-2f9a-7161-9c3f-58c36e2022e1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_01a15f0b-2f9a-79b8-b7a4-da1715897089" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-76b4-b170-a0357550b0b4" xlink:to="loc_srt_RangeAxis_01a15f0b-2f9a-79b8-b7a4-da1715897089" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a15f0b-2f9a-79b8-b7a4-da1715897089_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_01a15f0b-2f9a-79b8-b7a4-da1715897089" xlink:to="loc_srt_RangeMember_01a15f0b-2f9a-79b8-b7a4-da1715897089_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a15f0b-2f9a-7398-bea2-10132a394d2a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_01a15f0b-2f9a-79b8-b7a4-da1715897089" xlink:to="loc_srt_RangeMember_01a15f0b-2f9a-7398-bea2-10132a394d2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_01a15f0b-2f9a-71a6-a0d5-0d88a86b20e3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a15f0b-2f9a-7398-bea2-10132a394d2a" xlink:to="loc_srt_MinimumMember_01a15f0b-2f9a-71a6-a0d5-0d88a86b20e3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_01a15f0b-2f9a-77ba-a6a7-93ad9cfb13e4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a15f0b-2f9a-7398-bea2-10132a394d2a" xlink:to="loc_srt_MaximumMember_01a15f0b-2f9a-77ba-a6a7-93ad9cfb13e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_01a15f0b-2f9a-7b3a-b42d-abe688194156" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-781b-be1d-6736a6569bc0" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_01a15f0b-2f9a-7b3a-b42d-abe688194156" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_01a15f0b-2f9a-7f27-b9e7-02daeafc78ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-781b-be1d-6736a6569bc0" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_01a15f0b-2f9a-7f27-b9e7-02daeafc78ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a15f0b-2f9a-7e15-ac39-2a9cdd4adc14" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-781b-be1d-6736a6569bc0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a15f0b-2f9a-7e15-ac39-2a9cdd4adc14" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_01a15f0b-2f9a-73c8-bb62-e61701819874" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-781b-be1d-6736a6569bc0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_01a15f0b-2f9a-73c8-bb62-e61701819874" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisePrice_01a15f0b-2f9a-7cfd-b9e4-9c960f753b0d" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-781b-be1d-6736a6569bc0" xlink:to="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisePrice_01a15f0b-2f9a-7cfd-b9e4-9c960f753b0d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumAppreciationPerAward_01a15f0b-2f9a-77a4-9217-f76eacf6e19b" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumAppreciationPerAward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-781b-be1d-6736a6569bc0" xlink:to="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumAppreciationPerAward_01a15f0b-2f9a-77a4-9217-f76eacf6e19b" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/StockBasedCompensationValuationAssumptionsDetails" xlink:type="simple" xlink:href="pltr-20260930.xsd#StockBasedCompensationValuationAssumptionsDetails"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/StockBasedCompensationValuationAssumptionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-79cc-a2b0-00e96100c9ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-7a27-ad2b-15fe0c69e1c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-79cc-a2b0-00e96100c9ea" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-7a27-ad2b-15fe0c69e1c9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-705a-a3fc-e6d37e7c0fff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-7a27-ad2b-15fe0c69e1c9" xlink:to="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-705a-a3fc-e6d37e7c0fff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-705a-a3fc-e6d37e7c0fff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-705a-a3fc-e6d37e7c0fff" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-705a-a3fc-e6d37e7c0fff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-73ce-afbc-55bb7887b58a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-705a-a3fc-e6d37e7c0fff" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-73ce-afbc-55bb7887b58a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockAppreciationRightsSARSMember_01a15f0b-2f9a-72a8-9a40-599b5d94c1d8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockAppreciationRightsSARSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-73ce-afbc-55bb7887b58a" xlink:to="loc_us-gaap_StockAppreciationRightsSARSMember_01a15f0b-2f9a-72a8-9a40-599b5d94c1d8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_01a15f0b-2f9a-7606-a2b7-1f1369dcbf13" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-7a27-ad2b-15fe0c69e1c9" xlink:to="loc_srt_RangeAxis_01a15f0b-2f9a-7606-a2b7-1f1369dcbf13" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a15f0b-2f9a-7606-a2b7-1f1369dcbf13_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_01a15f0b-2f9a-7606-a2b7-1f1369dcbf13" xlink:to="loc_srt_RangeMember_01a15f0b-2f9a-7606-a2b7-1f1369dcbf13_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a15f0b-2f9a-77f1-be21-44fbfa9b8644" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_01a15f0b-2f9a-7606-a2b7-1f1369dcbf13" xlink:to="loc_srt_RangeMember_01a15f0b-2f9a-77f1-be21-44fbfa9b8644" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_01a15f0b-2f9a-795f-af56-30bbcbbe252e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a15f0b-2f9a-77f1-be21-44fbfa9b8644" xlink:to="loc_srt_MinimumMember_01a15f0b-2f9a-795f-af56-30bbcbbe252e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_01a15f0b-2f9a-7978-b164-6e2f9fdd74d9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a15f0b-2f9a-77f1-be21-44fbfa9b8644" xlink:to="loc_srt_MaximumMember_01a15f0b-2f9a-7978-b164-6e2f9fdd74d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueAxis_01a1690f-c033-7ad3-8abe-5b26267f6b4e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-7a27-ad2b-15fe0c69e1c9" xlink:to="loc_us-gaap_ValuationTechniqueAxis_01a1690f-c033-7ad3-8abe-5b26267f6b4e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDomain_01a1690f-c033-7ad3-8abe-5b26267f6b4e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationTechniqueAxis_01a1690f-c033-7ad3-8abe-5b26267f6b4e" xlink:to="loc_us-gaap_ValuationTechniqueDomain_01a1690f-c033-7ad3-8abe-5b26267f6b4e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDomain_01a16910-b53c-7e62-9ff6-d736fb07412b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationTechniqueAxis_01a1690f-c033-7ad3-8abe-5b26267f6b4e" xlink:to="loc_us-gaap_ValuationTechniqueDomain_01a16910-b53c-7e62-9ff6-d736fb07412b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueOptionPricingModelMember_01a16911-7ba8-766d-b5d2-9bd02ac0904a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueOptionPricingModelMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationTechniqueDomain_01a16910-b53c-7e62-9ff6-d736fb07412b" xlink:to="loc_us-gaap_ValuationTechniqueOptionPricingModelMember_01a16911-7ba8-766d-b5d2-9bd02ac0904a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MonteCarloModelMember_01a16912-2d84-74f7-a706-cf6c8f7aaf62" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MonteCarloModelMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationTechniqueDomain_01a16910-b53c-7e62-9ff6-d736fb07412b" xlink:to="loc_us-gaap_MonteCarloModelMember_01a16912-2d84-74f7-a706-cf6c8f7aaf62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_01a15f0b-2f9a-79ae-aef8-c79308736ea4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-79cc-a2b0-00e96100c9ea" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_01a15f0b-2f9a-79ae-aef8-c79308736ea4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_01a15f0b-2f9a-786c-86cd-401ab3ca9335" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-79cc-a2b0-00e96100c9ea" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_01a15f0b-2f9a-786c-86cd-401ab3ca9335" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsSuboptimalExerciseFactor_01a15f0b-2f9a-759d-a683-cecb0ff8bbc4" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsSuboptimalExerciseFactor"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-79cc-a2b0-00e96100c9ea" xlink:to="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsSuboptimalExerciseFactor_01a15f0b-2f9a-759d-a683-cecb0ff8bbc4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_01a15f0b-2f9a-761f-affb-bf04c0d1b5b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-79cc-a2b0-00e96100c9ea" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_01a15f0b-2f9a-761f-affb-bf04c0d1b5b9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_01a1691a-bafa-7750-88e7-84908d6f7bf1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-79cc-a2b0-00e96100c9ea" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_01a1691a-bafa-7750-88e7-84908d6f7bf1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_01a1691b-5333-7ff9-89b9-6253ebcbcef1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-79cc-a2b0-00e96100c9ea" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_01a1691b-5333-7ff9-89b9-6253ebcbcef1" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/StockBasedCompensationSummaryofRSUActivityDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#StockBasedCompensationSummaryofRSUActivityDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/StockBasedCompensationSummaryofRSUActivityDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-771e-b326-6e1d0acf6698" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-7b01-81b4-fc0d615b7af5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-771e-b326-6e1d0acf6698" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-7b01-81b4-fc0d615b7af5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-733d-96ae-a68c095dcfdd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-7b01-81b4-fc0d615b7af5" xlink:to="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-733d-96ae-a68c095dcfdd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-733d-96ae-a68c095dcfdd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-733d-96ae-a68c095dcfdd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-733d-96ae-a68c095dcfdd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7289-8dd7-2e008fd7c50c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_01a15f0b-2f9a-733d-96ae-a68c095dcfdd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7289-8dd7-2e008fd7c50c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_01a15f0b-2f9a-70d0-859d-d8123a2c8651" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7289-8dd7-2e008fd7c50c" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_01a15f0b-2f9a-70d0-859d-d8123a2c8651" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_01a15f0b-2f9a-7310-8217-3dd189e31021" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_01a15f0b-2f9a-7289-8dd7-2e008fd7c50c" xlink:to="loc_us-gaap_PerformanceSharesMember_01a15f0b-2f9a-7310-8217-3dd189e31021" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a15f0b-2f9a-769d-9060-d1489b200214" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-771e-b326-6e1d0acf6698" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a15f0b-2f9a-769d-9060-d1489b200214" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a15f0b-2f9a-7aeb-985f-83bc74c58b42" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a15f0b-2f9a-769d-9060-d1489b200214" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a15f0b-2f9a-7aeb-985f-83bc74c58b42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a15f0b-2f9a-76fe-b0da-7784aecdb852" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a15f0b-2f9a-769d-9060-d1489b200214" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_01a15f0b-2f9a-76fe-b0da-7784aecdb852" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a15f0b-2f9a-7fa2-aa1f-30794350532a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a15f0b-2f9a-769d-9060-d1489b200214" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_01a15f0b-2f9a-7fa2-aa1f-30794350532a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_01a15f0b-2f9a-7d61-9147-32f930e39e68" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a15f0b-2f9a-769d-9060-d1489b200214" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_01a15f0b-2f9a-7d61-9147-32f930e39e68" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdjustmentForPerformanceAchievement_01a15f0b-2f9a-7268-8cd7-1276f2bc25d7" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdjustmentForPerformanceAchievement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_01a15f0b-2f9a-769d-9060-d1489b200214" xlink:to="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdjustmentForPerformanceAchievement_01a15f0b-2f9a-7268-8cd7-1276f2bc25d7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_01a15f0b-2f9a-7238-9310-e8d0e004ded6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a15f0b-2f9a-7de8-8fdd-73e1cd09ae08" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-771e-b326-6e1d0acf6698" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a15f0b-2f9a-7de8-8fdd-73e1cd09ae08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a15f0b-2f9a-744f-970b-134e8c5cdf38" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a15f0b-2f9a-7de8-8fdd-73e1cd09ae08" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a15f0b-2f9a-744f-970b-134e8c5cdf38" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a15f0b-2f9a-77ae-8bb1-c69ecf06efc6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a15f0b-2f9a-7de8-8fdd-73e1cd09ae08" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_01a15f0b-2f9a-77ae-8bb1-c69ecf06efc6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_01a15f0b-2f9a-7d4f-9f02-53d9685737db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a15f0b-2f9a-7de8-8fdd-73e1cd09ae08" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_01a15f0b-2f9a-7d4f-9f02-53d9685737db" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_01a15f0b-2f9a-71c7-8a8e-2722c90948b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a15f0b-2f9a-7de8-8fdd-73e1cd09ae08" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_01a15f0b-2f9a-71c7-8a8e-2722c90948b7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdjustmentForPerformanceAchievementWeightedAverageGrantDateFairValue_01a15f0b-2f9a-7efa-a2d0-1ce591f99d59" xlink:href="pltr-20260930.xsd#pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdjustmentForPerformanceAchievementWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_01a15f0b-2f9a-7de8-8fdd-73e1cd09ae08" xlink:to="loc_pltr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdjustmentForPerformanceAchievementWeightedAverageGrantDateFairValue_01a15f0b-2f9a-7efa-a2d0-1ce591f99d59" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_01a15f0b-2f9a-7210-874b-69fc08de002c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/StockBasedCompensationSummaryofStockBasedCompensationExpenseDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#StockBasedCompensationSummaryofStockBasedCompensationExpenseDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/StockBasedCompensationSummaryofStockBasedCompensationExpenseDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7502-8e29-29c409892516" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-744a-8e5b-b81c8afedc87" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7502-8e29-29c409892516" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-744a-8e5b-b81c8afedc87" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_01a15f0b-2f9a-76dc-b4e4-8c4f5d3878aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementOfIncomeLocationBalanceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-744a-8e5b-b81c8afedc87" xlink:to="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_01a15f0b-2f9a-76dc-b4e4-8c4f5d3878aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_01a15f0b-2f9a-7541-86d6-2305e450c280" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7502-8e29-29c409892516" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_01a15f0b-2f9a-7541-86d6-2305e450c280" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/StockBasedCompensationSummaryofStockBasedCompensationExpenseDetail_1" xlink:type="simple" xlink:href="pltr-20260930.xsd#StockBasedCompensationSummaryofStockBasedCompensationExpenseDetail_1"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/StockBasedCompensationSummaryofStockBasedCompensationExpenseDetail_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7502-8e29-29c409892516" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-744a-8e5b-b81c8afedc87" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7502-8e29-29c409892516" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_01a15f0b-2f9a-744a-8e5b-b81c8afedc87" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_01a15f0b-2f9a-7541-86d6-2305e450c280" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_01a15f0b-2f9a-7502-8e29-29c409892516" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_01a15f0b-2f9a-7541-86d6-2305e450c280" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/EarningsPerShareAttributabletoCommonStockholdersAdditionalInformationDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#EarningsPerShareAttributabletoCommonStockholdersAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/EarningsPerShareAttributabletoCommonStockholdersAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_01a15f0b-2f9a-73c3-a06a-793b37bf2d2a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_01a15f0b-2f9a-7524-97bb-4771e8f42fb2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_01a15f0b-2f9a-73c3-a06a-793b37bf2d2a" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_01a15f0b-2f9a-7524-97bb-4771e8f42fb2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_01a15f0b-2f9a-7cb2-a35f-36b87c6c7ce7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_01a15f0b-2f9a-7524-97bb-4771e8f42fb2" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_01a15f0b-2f9a-7cb2-a35f-36b87c6c7ce7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_01a15f0b-2f9a-7cb2-a35f-36b87c6c7ce7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_01a15f0b-2f9a-7cb2-a35f-36b87c6c7ce7" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_01a15f0b-2f9a-7cb2-a35f-36b87c6c7ce7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_01a15f0b-2f9a-70a8-9792-0cf76389473a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_01a15f0b-2f9a-7cb2-a35f-36b87c6c7ce7" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_01a15f0b-2f9a-70a8-9792-0cf76389473a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_01a15f0b-2f9a-7947-8922-63a02be373c3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_01a15f0b-2f9a-70a8-9792-0cf76389473a" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_01a15f0b-2f9a-7947-8922-63a02be373c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockAppreciationRightsSARSMember_01a15f0b-2f9a-7235-a01f-f10e8cc2b367" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockAppreciationRightsSARSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_01a15f0b-2f9a-70a8-9792-0cf76389473a" xlink:to="loc_us-gaap_StockAppreciationRightsSARSMember_01a15f0b-2f9a-7235-a01f-f10e8cc2b367" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_01a15f0b-2f9a-7e10-8d8c-a34bda4c342b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_01a15f0b-2f9a-73c3-a06a-793b37bf2d2a" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_01a15f0b-2f9a-7e10-8d8c-a34bda4c342b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/SegmentandGeographicInformationSummaryofFinancialInformationforEachReportableSegmentDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#SegmentandGeographicInformationSummaryofFinancialInformationforEachReportableSegmentDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/SegmentandGeographicInformationSummaryofFinancialInformationforEachReportableSegmentDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-787b-9e84-77a61c05b81f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a15f0b-2f9a-742c-afbb-c0e093ad1d49" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-787b-9e84-77a61c05b81f" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a15f0b-2f9a-742c-afbb-c0e093ad1d49" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_01a15f0b-2f9a-721e-86d3-a37c9139a77c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a15f0b-2f9a-742c-afbb-c0e093ad1d49" xlink:to="loc_srt_ConsolidationItemsAxis_01a15f0b-2f9a-721e-86d3-a37c9139a77c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a15f0b-2f9a-721e-86d3-a37c9139a77c_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_01a15f0b-2f9a-721e-86d3-a37c9139a77c" xlink:to="loc_srt_ConsolidationItemsDomain_01a15f0b-2f9a-721e-86d3-a37c9139a77c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a15f0b-2f9a-7fa2-b5d3-6a41990ca020" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_01a15f0b-2f9a-721e-86d3-a37c9139a77c" xlink:to="loc_srt_ConsolidationItemsDomain_01a15f0b-2f9a-7fa2-b5d3-6a41990ca020" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_01a15f0b-2f9a-72a5-b7f5-c48584610f0b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_01a15f0b-2f9a-7fa2-b5d3-6a41990ca020" xlink:to="loc_us-gaap_OperatingSegmentsMember_01a15f0b-2f9a-72a5-b7f5-c48584610f0b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_01a15f0b-2f9a-714a-aa08-53fbe83fdedb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a15f0b-2f9a-742c-afbb-c0e093ad1d49" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_01a15f0b-2f9a-714a-aa08-53fbe83fdedb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a15f0b-2f9a-714a-aa08-53fbe83fdedb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a15f0b-2f9a-714a-aa08-53fbe83fdedb" xlink:to="loc_us-gaap_SegmentDomain_01a15f0b-2f9a-714a-aa08-53fbe83fdedb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_01a15f0b-2f9a-772e-a20a-edeef529ebd4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_01a15f0b-2f9a-714a-aa08-53fbe83fdedb" xlink:to="loc_us-gaap_SegmentDomain_01a15f0b-2f9a-772e-a20a-edeef529ebd4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_GovernmentOperatingSegmentMember_01a15f0b-2f9a-74a1-8f35-88a3ad5180f6" xlink:href="pltr-20260930.xsd#pltr_GovernmentOperatingSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a15f0b-2f9a-772e-a20a-edeef529ebd4" xlink:to="loc_pltr_GovernmentOperatingSegmentMember_01a15f0b-2f9a-74a1-8f35-88a3ad5180f6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_CommercialMember_01a15f0b-2f9a-72e3-99ef-8a41ba9ba39d" xlink:href="pltr-20260930.xsd#pltr_CommercialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_01a15f0b-2f9a-772e-a20a-edeef529ebd4" xlink:to="loc_pltr_CommercialMember_01a15f0b-2f9a-72e3-99ef-8a41ba9ba39d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_01a15f0b-2f9a-7505-921c-257dec6eeb8d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-787b-9e84-77a61c05b81f" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_01a15f0b-2f9a-7505-921c-257dec6eeb8d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingOtherItemAmount_01a15f0b-2f9a-7db6-8546-01f6babd4679" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingOtherItemAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-787b-9e84-77a61c05b81f" xlink:to="loc_us-gaap_SegmentReportingOtherItemAmount_01a15f0b-2f9a-7db6-8546-01f6babd4679" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_Contribution_01a15f0b-2f9a-7ed8-935d-fc803b02e927" xlink:href="pltr-20260930.xsd#pltr_Contribution"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-787b-9e84-77a61c05b81f" xlink:to="loc_pltr_Contribution_01a15f0b-2f9a-7ed8-935d-fc803b02e927" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ContributionMargin_01a15f0b-2f9a-7ad1-a6ff-06fa66dc84bf" xlink:href="pltr-20260930.xsd#pltr_ContributionMargin"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-787b-9e84-77a61c05b81f" xlink:to="loc_pltr_ContributionMargin_01a15f0b-2f9a-7ad1-a6ff-06fa66dc84bf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_NumberOfReportableSegmentsNotDisclosedFlag_01a179f9-ef4b-7eac-b0cc-7dac19998415" xlink:href="pltr-20260930.xsd#pltr_NumberOfReportableSegmentsNotDisclosedFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-787b-9e84-77a61c05b81f" xlink:to="loc_pltr_NumberOfReportableSegmentsNotDisclosedFlag_01a179f9-ef4b-7eac-b0cc-7dac19998415" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/SegmentandGeographicInformationSummaryofReconciliationofSegmentFinancialInformationtoLossfromOperationsDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#SegmentandGeographicInformationSummaryofReconciliationofSegmentFinancialInformationtoLossfromOperationsDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/SegmentandGeographicInformationSummaryofReconciliationofSegmentFinancialInformationtoLossfromOperationsDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-7190-ab0b-9e1d85feee90" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a15f0b-2f9a-7d9d-9ac4-55dc260f6f6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-7190-ab0b-9e1d85feee90" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a15f0b-2f9a-7d9d-9ac4-55dc260f6f6b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_01a15f0b-2f9a-7344-be3e-32ac8aa324af" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_01a15f0b-2f9a-7d9d-9ac4-55dc260f6f6b" xlink:to="loc_srt_ConsolidationItemsAxis_01a15f0b-2f9a-7344-be3e-32ac8aa324af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a15f0b-2f9a-7344-be3e-32ac8aa324af_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_01a15f0b-2f9a-7344-be3e-32ac8aa324af" xlink:to="loc_srt_ConsolidationItemsDomain_01a15f0b-2f9a-7344-be3e-32ac8aa324af_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_01a15f0b-2f9a-7f3b-b3d9-488e171c9581" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_01a15f0b-2f9a-7344-be3e-32ac8aa324af" xlink:to="loc_srt_ConsolidationItemsDomain_01a15f0b-2f9a-7f3b-b3d9-488e171c9581" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MaterialReconcilingItemsMember_01a15f0b-2f9a-78a8-a630-4a39a4a7466f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MaterialReconcilingItemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_01a15f0b-2f9a-7f3b-b3d9-488e171c9581" xlink:to="loc_us-gaap_MaterialReconcilingItemsMember_01a15f0b-2f9a-78a8-a630-4a39a4a7466f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_01a15f0b-2f9a-7014-8a65-2ab1ac4484d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_01a15f0b-2f9a-7f3b-b3d9-488e171c9581" xlink:to="loc_us-gaap_OperatingSegmentsMember_01a15f0b-2f9a-7014-8a65-2ab1ac4484d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_01a15f0b-2f9a-7104-ae30-54fe3d81a4e2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-7190-ab0b-9e1d85feee90" xlink:to="loc_us-gaap_OperatingIncomeLoss_01a15f0b-2f9a-7104-ae30-54fe3d81a4e2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ResearchAndDevelopmentExpenseExcludingStockbasedCompensationExpense_01a15f0b-2f9a-7ac5-b31c-4efc983903d6" xlink:href="pltr-20260930.xsd#pltr_ResearchAndDevelopmentExpenseExcludingStockbasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-7190-ab0b-9e1d85feee90" xlink:to="loc_pltr_ResearchAndDevelopmentExpenseExcludingStockbasedCompensationExpense_01a15f0b-2f9a-7ac5-b31c-4efc983903d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_GeneralAndAdministrativeExpenseExcludingStockbasedCompensationExpense_01a15f0b-2f9a-7142-bf5c-aeb670fd8a9e" xlink:href="pltr-20260930.xsd#pltr_GeneralAndAdministrativeExpenseExcludingStockbasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-7190-ab0b-9e1d85feee90" xlink:to="loc_pltr_GeneralAndAdministrativeExpenseExcludingStockbasedCompensationExpense_01a15f0b-2f9a-7142-bf5c-aeb670fd8a9e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_01a15f0b-2f9a-7417-ab0a-dd3fba01d5e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-7190-ab0b-9e1d85feee90" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_01a15f0b-2f9a-7417-ab0a-dd3fba01d5e7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_Contribution_01a15f0b-2f9a-73dd-ba5a-d0fae5e19556" xlink:href="pltr-20260930.xsd#pltr_Contribution"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_01a15f0b-2f9a-7190-ab0b-9e1d85feee90" xlink:to="loc_pltr_Contribution_01a15f0b-2f9a-73dd-ba5a-d0fae5e19556" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/SegmentandGeographicInformationSummaryofRevenuebyGeographyDetail" xlink:type="simple" xlink:href="pltr-20260930.xsd#SegmentandGeographicInformationSummaryofRevenuebyGeographyDetail"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/SegmentandGeographicInformationSummaryofRevenuebyGeographyDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_01a15f0b-2f9a-7c73-b29f-72ed7b38b868" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_01a15f0b-2f9a-770d-a27e-5815255a6611" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_01a15f0b-2f9a-7c73-b29f-72ed7b38b868" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_01a15f0b-2f9a-770d-a27e-5815255a6611" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_01a15f0b-2f9a-7cdf-ae9c-9a2aa9532681" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_01a15f0b-2f9a-770d-a27e-5815255a6611" xlink:to="loc_srt_StatementGeographicalAxis_01a15f0b-2f9a-7cdf-ae9c-9a2aa9532681" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_01a15f0b-2f9a-7cdf-ae9c-9a2aa9532681_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_01a15f0b-2f9a-7cdf-ae9c-9a2aa9532681" xlink:to="loc_srt_SegmentGeographicalDomain_01a15f0b-2f9a-7cdf-ae9c-9a2aa9532681_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_01a15f0b-2f9a-7b8e-8ab2-d0af33ee4514" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_01a15f0b-2f9a-7cdf-ae9c-9a2aa9532681" xlink:to="loc_srt_SegmentGeographicalDomain_01a15f0b-2f9a-7b8e-8ab2-d0af33ee4514" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_01a15f0b-2f9a-7762-b14b-0287fa169e02" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_01a15f0b-2f9a-7b8e-8ab2-d0af33ee4514" xlink:to="loc_country_US_01a15f0b-2f9a-7762-b14b-0287fa169e02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_01a16570-5b9f-7af1-8c81-55d005c4569c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_01a15f0b-2f9a-7b8e-8ab2-d0af33ee4514" xlink:to="loc_us-gaap_NonUsMember_01a16570-5b9f-7af1-8c81-55d005c4569c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_01a15f0b-2f9a-73fa-868d-2bea8ba29a77" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_01a15f0b-2f9a-770d-a27e-5815255a6611" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_01a15f0b-2f9a-73fa-868d-2bea8ba29a77" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_01a15f0b-2f9a-73fa-868d-2bea8ba29a77_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_01a15f0b-2f9a-73fa-868d-2bea8ba29a77" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_01a15f0b-2f9a-73fa-868d-2bea8ba29a77_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_01a15f0b-2f9a-79e1-b699-2a3320ea838a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_01a15f0b-2f9a-73fa-868d-2bea8ba29a77" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_01a15f0b-2f9a-79e1-b699-2a3320ea838a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeographicConcentrationRiskMember_01a15f0b-2f9a-7d4a-8d18-e037d64e063c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeographicConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_01a15f0b-2f9a-79e1-b699-2a3320ea838a" xlink:to="loc_us-gaap_GeographicConcentrationRiskMember_01a15f0b-2f9a-7d4a-8d18-e037d64e063c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a15f0b-2f9a-7e95-976d-b3b6f8355136" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_01a15f0b-2f9a-770d-a27e-5815255a6611" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a15f0b-2f9a-7e95-976d-b3b6f8355136" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a15f0b-2f9a-7e95-976d-b3b6f8355136_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a15f0b-2f9a-7e95-976d-b3b6f8355136" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a15f0b-2f9a-7e95-976d-b3b6f8355136_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a15f0b-2f9a-7f6f-a121-30e4db42a84e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_01a15f0b-2f9a-7e95-976d-b3b6f8355136" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a15f0b-2f9a-7f6f-a121-30e4db42a84e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_01a15f0b-2f9a-747d-b0af-2815dd75e1f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_01a15f0b-2f9a-7f6f-a121-30e4db42a84e" xlink:to="loc_us-gaap_SalesRevenueNetMember_01a15f0b-2f9a-747d-b0af-2815dd75e1f1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_01a15f0b-2f9a-78c1-b6dc-d576840e5b22" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_01a15f0b-2f9a-770d-a27e-5815255a6611" xlink:to="loc_srt_RangeAxis_01a15f0b-2f9a-78c1-b6dc-d576840e5b22" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a15f0b-2f9a-78c1-b6dc-d576840e5b22_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_01a15f0b-2f9a-78c1-b6dc-d576840e5b22" xlink:to="loc_srt_RangeMember_01a15f0b-2f9a-78c1-b6dc-d576840e5b22_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_01a15f0b-2f9a-7ae1-b25f-638efe669be0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_01a15f0b-2f9a-78c1-b6dc-d576840e5b22" xlink:to="loc_srt_RangeMember_01a15f0b-2f9a-7ae1-b25f-638efe669be0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_01a15f0b-2f9a-7888-a0f0-179633ca4eae" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_01a15f0b-2f9a-7ae1-b25f-638efe669be0" xlink:to="loc_srt_MinimumMember_01a15f0b-2f9a-7888-a0f0-179633ca4eae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_01a15f0b-2f9a-7669-af7a-1d998a4d0a05" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_01a15f0b-2f9a-7c73-b29f-72ed7b38b868" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_01a15f0b-2f9a-7669-af7a-1d998a4d0a05" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_01a15f0b-2f9a-763a-9239-b7f2438f9e2e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_01a15f0b-2f9a-7c73-b29f-72ed7b38b868" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_01a15f0b-2f9a-763a-9239-b7f2438f9e2e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.palantir.com/role/RelatedPartyTransactionsDetails" xlink:type="simple" xlink:href="pltr-20260930.xsd#RelatedPartyTransactionsDetails"/>
  <link:definitionLink xlink:role="http://www.palantir.com/role/RelatedPartyTransactionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_01a179ed-c6c0-7094-aabd-b27afd2cc4ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_01a15f0b-2f9a-7736-a0f1-75ce7deae95b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_01a179ed-c6c0-7094-aabd-b27afd2cc4ff" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_01a15f0b-2f9a-7736-a0f1-75ce7deae95b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_01a179ed-c6c0-7a54-95d3-44e589794a11" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_01a15f0b-2f9a-7736-a0f1-75ce7deae95b" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_01a179ed-c6c0-7a54-95d3-44e589794a11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_01a179ed-c6c0-7a54-95d3-44e589794a11_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_01a179ed-c6c0-7a54-95d3-44e589794a11" xlink:to="loc_us-gaap_RelatedPartyDomain_01a179ed-c6c0-7a54-95d3-44e589794a11_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_01a179ed-c6c0-7d17-bac1-5ef12342ce96" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_01a179ed-c6c0-7a54-95d3-44e589794a11" xlink:to="loc_us-gaap_RelatedPartyDomain_01a179ed-c6c0-7d17-bac1-5ef12342ce96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ChiefExecutiveOfficerMember_01a179ed-c6c0-79b4-be1f-16f6b60fd6ea" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ChiefExecutiveOfficerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_01a179ed-c6c0-7d17-bac1-5ef12342ce96" xlink:to="loc_srt_ChiefExecutiveOfficerMember_01a179ed-c6c0-79b4-be1f-16f6b60fd6ea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_01a179ed-c6c0-7ad4-9ce0-5acb6598915c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_01a179ed-c6c0-7094-aabd-b27afd2cc4ff" xlink:to="loc_us-gaap_OperatingExpenses_01a179ed-c6c0-7ad4-9ce0-5acb6598915c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/TradingArrangementsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#TradingArrangmentsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/TradingArrangementsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllTradingArrangementsMember" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#ecd_AllTradingArrangementsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShyamSankarAugust292025PlanMember_01a15f0b-2dbf-7713-9fd6-3ff78e7655ff" xlink:href="pltr-20260930.xsd#pltr_ShyamSankarAugust292025PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_pltr_ShyamSankarAugust292025PlanMember_01a15f0b-2dbf-7713-9fd6-3ff78e7655ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShyamSankarAugust102026PlanMember_01a177b6-c5e1-7fb9-8ec3-15b7800c3b70" xlink:href="pltr-20260930.xsd#pltr_ShyamSankarAugust102026PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_pltr_ShyamSankarAugust102026PlanMember_01a177b6-c5e1-7fb9-8ec3-15b7800c3b70" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_DavidGlazerMarch162026PlanMember_01a177bb-bad8-752b-93c5-4c1424affb12" xlink:href="pltr-20260930.xsd#pltr_DavidGlazerMarch162026PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_pltr_DavidGlazerMarch162026PlanMember_01a177bb-bad8-752b-93c5-4c1424affb12" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_DavidGlazerSeptember162026PlanMember_01a177bd-e392-701a-a950-533baba350fc" xlink:href="pltr-20260930.xsd#pltr_DavidGlazerSeptember162026PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllTradingArrangementsMember" xlink:to="loc_pltr_DavidGlazerSeptember162026PlanMember_01a177bd-e392-701a-a950-533baba350fc" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_ShyamSankarMember_01a15f0b-2dbf-7ac7-aa8e-e17347357858" xlink:href="pltr-20260930.xsd#pltr_ShyamSankarMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_pltr_ShyamSankarMember_01a15f0b-2dbf-7ac7-aa8e-e17347357858" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_DavidGlazerMember_01a15f0b-2dbf-768f-98c7-f4841a0a6b13" xlink:href="pltr-20260930.xsd#pltr_DavidGlazerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_pltr_DavidGlazerMember_01a15f0b-2dbf-768f-98c7-f4841a0a6b13" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_PeterThielMember_01a169cb-3d35-7666-a07f-47ad5f5bbab0" xlink:href="pltr-20260930.xsd#pltr_PeterThielMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_pltr_PeterThielMember_01a169cb-3d35-7666-a07f-47ad5f5bbab0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_AlexanderKarpMember_01a169d9-30a3-7153-8b32-38b25bb8c038" xlink:href="pltr-20260930.xsd#pltr_AlexanderKarpMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_pltr_AlexanderKarpMember_01a169d9-30a3-7153-8b32-38b25bb8c038" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_LaurenStatMember_01a15f0b-2dbf-7df5-bdf6-0cad959fe2ec" xlink:href="pltr-20260930.xsd#pltr_LaurenStatMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_pltr_LaurenStatMember_01a15f0b-2dbf-7df5-bdf6-0cad959fe2ec" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_pltr_RyanTaylorMember_01a15f0b-2dbf-7f47-b7ed-e67438436abf" xlink:href="pltr-20260930.xsd#pltr_RyanTaylorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_pltr_RyanTaylorMember_01a15f0b-2dbf-7f47-b7ed-e67438436abf" xlink:type="arc" order="7"/>
  </link:definitionLink>
</link:linkbase>
