diff --git a/clang/lib/Basic/Targets/OSTargets.h b/clang/lib/Basic/Targets/OSTargets.h
index 342af4bbc42b7..4366c1149e405 100644
--- a/clang/lib/Basic/Targets/OSTargets.h
+++ b/clang/lib/Basic/Targets/OSTargets.h
@@ -74,7 +74,8 @@ class LLVM_LIBRARY_VISIBILITY DarwinTargetInfo : public OSTargetInfo<Target> {
         this->TLSSupported = !Triple.isOSVersionLT(3);
     } else if (Triple.isDriverKit()) {
       // No TLS on DriverKit.
-    }
+    } else if (Triple.isXROS())
+      this->TLSSupported = true;
 
     this->MCountName = "\01mcount";
   }
@@ -109,6 +110,9 @@ class LLVM_LIBRARY_VISIBILITY DarwinTargetInfo : public OSTargetInfo<Target> {
     case llvm::Triple::WatchOS: // Earliest supporting version is 5.0.0.
       MinVersion = llvm::VersionTuple(5U);
       break;
+    case llvm::Triple::XROS:
+      MinVersion = llvm::VersionTuple(0);
+      break;
     default:
       // Conservatively return 8 bytes if OS is unknown.
       return 64;
diff --git a/clang/lib/CodeGen/CGObjC.cpp b/clang/lib/CodeGen/CGObjC.cpp
index acc85165a470b..03fc0ec7ff54e 100644
--- a/clang/lib/CodeGen/CGObjC.cpp
+++ b/clang/lib/CodeGen/CGObjC.cpp
@@ -3941,6 +3941,8 @@ static unsigned getBaseMachOPlatformID(const llvm::Triple &TT) {
     return llvm::MachO::PLATFORM_TVOS;
   case llvm::Triple::WatchOS:
     return llvm::MachO::PLATFORM_WATCHOS;
+  case llvm::Triple::XROS:
+    return llvm::MachO::PLATFORM_XROS;
   case llvm::Triple::DriverKit:
     return llvm::MachO::PLATFORM_DRIVERKIT;
   default:
@@ -4024,6 +4026,9 @@ static bool isFoundationNeededForDarwinAvailabilityCheck(
   case llvm::Triple::MacOSX:
     FoundationDroppedInVersion = VersionTuple(/*Major=*/10, /*Minor=*/15);
     break;
+  case llvm::Triple::XROS:
+    // XROS doesn't need Foundation.
+    return false;
   case llvm::Triple::DriverKit:
     // DriverKit doesn't need Foundation.
     return false;
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 1889ea28079df..35d563b9a87fa 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -6213,6 +6213,7 @@ const ToolChain &Driver::getToolChain(const ArgList &Args,
     case llvm::Triple::IOS:
     case llvm::Triple::TvOS:
     case llvm::Triple::WatchOS:
+    case llvm::Triple::XROS:
     case llvm::Triple::DriverKit:
       TC = std::make_unique<toolchains::DarwinClang>(*this, Target, Args);
       break;
diff --git a/clang/lib/Driver/ToolChains/Arch/AArch64.cpp b/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
index 85f053dc8b6ea..0cf96bb5c9cb0 100644
--- a/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
@@ -53,6 +53,11 @@ std::string aarch64::getAArch64TargetCPU(const ArgList &Args,
     return "apple-m1";
   }
 
+  if (Triple.isXROS()) {
+    // The xrOS simulator runs on M1 as well, it should have been covered above.
+    assert(!Triple.isSimulatorEnvironment() && "xrossim should be mac-like");
+    return "apple-a12";
+  }
   // arm64e requires v8.3a and only runs on apple-a12 and later CPUs.
   if (Triple.isArm64e())
     return "apple-a12";
diff --git a/clang/lib/Driver/ToolChains/Arch/ARM.cpp b/clang/lib/Driver/ToolChains/Arch/ARM.cpp
index 25470db2b6ceb..e6ee2f88a84ed 100644
--- a/clang/lib/Driver/ToolChains/Arch/ARM.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/ARM.cpp
@@ -367,6 +367,7 @@ arm::FloatABI arm::getDefaultFloatABI(const llvm::Triple &Triple) {
   case llvm::Triple::IOS:
   case llvm::Triple::TvOS:
   case llvm::Triple::DriverKit:
+  case llvm::Triple::XROS:
     // Darwin defaults to "softfp" for v6 and v7.
     if (Triple.isWatchABI())
       return FloatABI::Hard;
@@ -836,8 +837,8 @@ llvm::ARM::FPUKind arm::getARMTargetFeatures(const Driver &D,
     if (A->getOption().matches(options::OPT_mlong_calls))
       Features.push_back("+long-calls");
   } else if (KernelOrKext && (!Triple.isiOS() || Triple.isOSVersionLT(6)) &&
-             !Triple.isWatchOS()) {
-      Features.push_back("+long-calls");
+             !Triple.isWatchOS() && !Triple.isXROS()) {
+    Features.push_back("+long-calls");
   }
 
   // Generate execute-only output (no data access to code sections).
diff --git a/clang/lib/Driver/ToolChains/Darwin.cpp b/clang/lib/Driver/ToolChains/Darwin.cpp
index 8f24e5287e198..9050c545cf544 100644
--- a/clang/lib/Driver/ToolChains/Darwin.cpp
+++ b/clang/lib/Driver/ToolChains/Darwin.cpp
@@ -219,7 +219,8 @@ static bool shouldLinkerNotDedup(bool IsLinkerOnlyAction, const ArgList &Args) {
 void darwin::Linker::AddLinkArgs(Compilation &C, const ArgList &Args,
                                  ArgStringList &CmdArgs,
                                  const InputInfoList &Inputs,
-                                 VersionTuple Version, bool LinkerIsLLD) const {
+                                 VersionTuple Version, bool LinkerIsLLD,
+                                 bool UsePlatformVersion) const {
   const Driver &D = getToolChain().getDriver();
   const toolchains::MachO &MachOTC = getMachOToolChain();
 
@@ -355,7 +356,7 @@ void darwin::Linker::AddLinkArgs(Compilation &C, const ArgList &Args,
   Args.AddAllArgs(CmdArgs, options::OPT_init);
 
   // Add the deployment target.
-  if (Version >= VersionTuple(520) || LinkerIsLLD)
+  if (Version >= VersionTuple(520) || LinkerIsLLD || UsePlatformVersion)
     MachOTC.addPlatformVersionArgs(Args, CmdArgs);
   else
     MachOTC.addMinVersionArgs(Args, CmdArgs);
@@ -596,9 +597,13 @@ void darwin::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   const char *Exec =
       Args.MakeArgString(getToolChain().GetLinkerPath(&LinkerIsLLD));
 
+  // xrOS always uses -platform-version.
+  bool UsePlatformVersion = getToolChain().getTriple().isXROS();
+
   // I'm not sure why this particular decomposition exists in gcc, but
   // we follow suite for ease of comparison.
-  AddLinkArgs(C, Args, CmdArgs, Inputs, Version, LinkerIsLLD);
+  AddLinkArgs(C, Args, CmdArgs, Inputs, Version, LinkerIsLLD,
+              UsePlatformVersion);
 
   if (willEmitRemarks(Args) &&
       checkRemarksOptions(getToolChain().getDriver(), Args,
@@ -954,6 +959,13 @@ ObjCRuntime Darwin::getDefaultObjCRuntime(bool isNonFragile) const {
     return ObjCRuntime(ObjCRuntime::WatchOS, TargetVersion);
   if (isTargetIOSBased())
     return ObjCRuntime(ObjCRuntime::iOS, TargetVersion);
+  if (isTargetXROS()) {
+    // XROS uses the iOS runtime.
+    auto T = llvm::Triple(Twine("arm64-apple-") +
+                          llvm::Triple::getOSTypeName(llvm::Triple::XROS) +
+                          TargetVersion.getAsString());
+    return ObjCRuntime(ObjCRuntime::iOS, T.getiOSVersion());
+  }
   if (isNonFragile)
     return ObjCRuntime(ObjCRuntime::MacOSX, TargetVersion);
   return ObjCRuntime(ObjCRuntime::FragileMacOSX, TargetVersion);
@@ -961,7 +973,7 @@ ObjCRuntime Darwin::getDefaultObjCRuntime(bool isNonFragile) const {
 
 /// Darwin provides a blocks runtime starting in MacOS X 10.6 and iOS 3.2.
 bool Darwin::hasBlocksRuntime() const {
-  if (isTargetWatchOSBased() || isTargetDriverKit())
+  if (isTargetWatchOSBased() || isTargetDriverKit() || isTargetXROS())
     return true;
   else if (isTargetIOSBased())
     return !isIPhoneOSVersionLT(3, 2);
@@ -1092,6 +1104,8 @@ std::string Darwin::ComputeEffectiveClangTriple(const ArgList &Args,
     Str += "driverkit";
   else if (isTargetIOSBased() || isTargetMacCatalyst())
     Str += "ios";
+  else if (isTargetXROS())
+    Str += llvm::Triple::getOSTypeName(llvm::Triple::XROS);
   else
     Str += "macosx";
   Str += getTripleTargetVersion().getAsString();
@@ -1174,6 +1188,8 @@ void DarwinClang::AddLinkARCArgs(const ArgList &Args,
   // ARC runtime is supported everywhere on arm64e.
   if (getTriple().isArm64e())
     return;
+  if (isTargetXROS())
+    return;
 
   ObjCRuntime runtime = getDefaultObjCRuntime(/*nonfragile*/ true);
 
@@ -1309,6 +1325,8 @@ StringRef Darwin::getPlatformFamily() const {
       return "Watch";
     case DarwinPlatformKind::DriverKit:
       return "DriverKit";
+    case DarwinPlatformKind::XROS:
+      return "XR";
   }
   llvm_unreachable("Unsupported platform");
 }
@@ -1340,6 +1358,9 @@ StringRef Darwin::getOSLibraryNameSuffix(bool IgnoreSim) const {
   case DarwinPlatformKind::WatchOS:
     return TargetEnvironment == NativeEnvironment || IgnoreSim ? "watchos"
                                                                : "watchossim";
+  case DarwinPlatformKind::XROS:
+    return TargetEnvironment == NativeEnvironment || IgnoreSim ? "xros"
+                                                               : "xrossim";
   case DarwinPlatformKind::DriverKit:
     return "driverkit";
   }
@@ -1649,6 +1670,9 @@ struct DarwinPlatform {
     case DarwinPlatformKind::WatchOS:
       Opt = options::OPT_mwatchos_version_min_EQ;
       break;
+    case DarwinPlatformKind::XROS:
+      // xrOS always explicitly provides a version in the triple.
+      return;
     case DarwinPlatformKind::DriverKit:
       // DriverKit always explicitly provides a version in the triple.
       return;
@@ -1794,6 +1818,8 @@ struct DarwinPlatform {
       return DarwinPlatformKind::TvOS;
     case llvm::Triple::WatchOS:
       return DarwinPlatformKind::WatchOS;
+    case llvm::Triple::XROS:
+      return DarwinPlatformKind::XROS;
     case llvm::Triple::DriverKit:
       return DarwinPlatformKind::DriverKit;
     default:
@@ -1975,6 +2001,10 @@ inferDeploymentTargetFromSDK(DerivedArgList &Args,
       return DarwinPlatform::createFromSDK(
           Darwin::TvOS, Version,
           /*IsSimulator=*/SDK.starts_with("AppleTVSimulator"));
+    else if (SDK.starts_with("XR"))
+      return DarwinPlatform::createFromSDK(
+          Darwin::XROS, Version,
+          /*IsSimulator=*/SDK.contains("Simulator"));
     else if (SDK.starts_with("DriverKit"))
       return DarwinPlatform::createFromSDK(Darwin::DriverKit, Version);
     return std::nullopt;
@@ -2013,6 +2043,11 @@ std::string getOSVersion(llvm::Triple::OSType OS, const llvm::Triple &Triple,
   case llvm::Triple::WatchOS:
     OsVersion = Triple.getWatchOSVersion();
     break;
+  case llvm::Triple::XROS:
+    OsVersion = Triple.getOSVersion();
+    if (!OsVersion.getMajor())
+      OsVersion = OsVersion.withMajorReplaced(1);
+    break;
   case llvm::Triple::DriverKit:
     OsVersion = Triple.getDriverKitVersion();
     break;
@@ -2104,6 +2139,7 @@ std::optional<DarwinPlatform> getDeploymentTargetFromMTargetOSArg(
   case llvm::Triple::IOS:
   case llvm::Triple::TvOS:
   case llvm::Triple::WatchOS:
+  case llvm::Triple::XROS:
     break;
   default:
     TheDriver.Diag(diag::err_drv_invalid_os_in_arg)
@@ -2319,6 +2355,13 @@ void Darwin::AddDeploymentTarget(DerivedArgList &Args) const {
         Micro >= 100)
       getDriver().Diag(diag::err_drv_invalid_version_number)
           << OSTarget->getAsString(Args, Opts);
+  } else if (Platform == XROS) {
+    if (!Driver::GetReleaseVersion(OSTarget->getOSVersion(), Major, Minor,
+                                   Micro, HadExtra) ||
+        HadExtra || Major < 1 || Major >= MajorVersionLimit || Minor >= 100 ||
+        Micro >= 100)
+      getDriver().Diag(diag::err_drv_invalid_version_number)
+          << OSTarget->getAsString(Args, Opts);
   } else
     llvm_unreachable("unknown kind of Darwin platform");
 
@@ -2641,6 +2684,10 @@ void DarwinClang::AddCCKextLibArgs(const ArgList &Args,
     llvm::sys::path::append(P, "libclang_rt.cc_kext_ios.a");
   } else if (isTargetDriverKit()) {
     // DriverKit doesn't want extra runtime support.
+  } else if (isTargetXROSDevice()) {
+    llvm::sys::path::append(
+        P, llvm::Twine("libclang_rt.cc_kext_") +
+               llvm::Triple::getOSTypeName(llvm::Triple::XROS) + ".a");
   } else {
     llvm::sys::path::append(P, "libclang_rt.cc_kext.a");
   }
@@ -2855,6 +2902,8 @@ bool Darwin::isAlignedAllocationUnavailable() const {
   case WatchOS: // Earlier than 4.0.
     OS = llvm::Triple::WatchOS;
     break;
+  case XROS: // Always available.
+    return false;
   case DriverKit: // Always available.
     return false;
   }
@@ -2876,6 +2925,8 @@ static bool sdkSupportsBuiltinModules(const Darwin::DarwinPlatformKind &TargetPl
     return SDKVersion >= VersionTuple(99U);
   case Darwin::WatchOS:
     return SDKVersion >= VersionTuple(99U);
+  case Darwin::XROS:
+    return SDKVersion >= VersionTuple(99U);
   default:
     return true;
   }
@@ -2998,7 +3049,7 @@ Darwin::TranslateArgs(const DerivedArgList &Args, StringRef BoundArch,
   // FIXME: It would be far better to avoid inserting those -static arguments,
   // but we can't check the deployment target in the translation code until
   // it is set here.
-  if (isTargetWatchOSBased() || isTargetDriverKit() ||
+  if (isTargetWatchOSBased() || isTargetDriverKit() || isTargetXROS() ||
       (isTargetIOSBased() && !isIPhoneOSVersionLT(6, 0))) {
     for (ArgList::iterator it = DAL->begin(), ie = DAL->end(); it != ie; ) {
       Arg *A = *it;
@@ -3092,6 +3143,8 @@ void Darwin::addMinVersionArgs(const ArgList &Args,
                                ArgStringList &CmdArgs) const {
   VersionTuple TargetVersion = getTripleTargetVersion();
 
+  assert(!isTargetXROS() && "xrOS always uses -platform-version");
+
   if (isTargetWatchOS())
     CmdArgs.push_back("-watchos_version_min");
   else if (isTargetWatchOSSimulator())
@@ -3151,6 +3204,8 @@ static const char *getPlatformName(Darwin::DarwinPlatformKind Platform,
     return "tvos";
   case Darwin::WatchOS:
     return "watchos";
+  case Darwin::XROS:
+    return "xros";
   case Darwin::DriverKit:
     return "driverkit";
   }
@@ -3347,7 +3402,7 @@ void Darwin::addStartObjectFileArgs(const ArgList &Args,
 }
 
 void Darwin::CheckObjCARC() const {
-  if (isTargetIOSBased() || isTargetWatchOSBased() ||
+  if (isTargetIOSBased() || isTargetWatchOSBased() || isTargetXROS() ||
       (isTargetMacOSBased() && !isMacosxVersionLT(10, 6)))
     return;
   getDriver().Diag(diag::err_arc_unsupported_on_toolchain);
diff --git a/clang/lib/Driver/ToolChains/Darwin.h b/clang/lib/Driver/ToolChains/Darwin.h
index 815449ae8f379..fda3b1a3639a8 100644
--- a/clang/lib/Driver/ToolChains/Darwin.h
+++ b/clang/lib/Driver/ToolChains/Darwin.h
@@ -65,7 +65,7 @@ class LLVM_LIBRARY_VISIBILITY Linker : public MachOTool {
   void AddLinkArgs(Compilation &C, const llvm::opt::ArgList &Args,
                    llvm::opt::ArgStringList &CmdArgs,
                    const InputInfoList &Inputs, VersionTuple Version,
-                   bool LinkerIsLLD) const;
+                   bool LinkerIsLLD, bool UsePlatformVersion) const;
 
 public:
   Linker(const ToolChain &TC) : MachOTool("darwin::Linker", "linker", TC) {}
@@ -298,6 +298,7 @@ class LLVM_LIBRARY_VISIBILITY Darwin : public MachO {
     TvOS,
     WatchOS,
     DriverKit,
+    XROS,
     LastDarwinPlatform = DriverKit
   };
   enum DarwinEnvironmentKind {
@@ -404,6 +405,16 @@ class LLVM_LIBRARY_VISIBILITY Darwin : public MachO {
     return isTargetIPhoneOS() || isTargetIOSSimulator();
   }
 
+  bool isTargetXROSDevice() const {
+    return TargetPlatform == XROS && TargetEnvironment == NativeEnvironment;
+  }
+
+  bool isTargetXROSSimulator() const {
+    return TargetPlatform == XROS && TargetEnvironment == Simulator;
+  }
+
+  bool isTargetXROS() const { return TargetPlatform == XROS; }
+
   bool isTargetTvOS() const {
     assert(TargetInitialized && "Target not initialized!");
     return TargetPlatform == TvOS && TargetEnvironment == NativeEnvironment;
@@ -546,7 +557,8 @@ class LLVM_LIBRARY_VISIBILITY Darwin : public MachO {
   GetDefaultStackProtectorLevel(bool KernelOrKext) const override {
     // Stack protectors default to on for user code on 10.5,
     // and for everything in 10.6 and beyond
-    if (isTargetIOSBased() || isTargetWatchOSBased() || isTargetDriverKit())
+    if (isTargetIOSBased() || isTargetWatchOSBased() || isTargetDriverKit() ||
+        isTargetXROS())
       return LangOptions::SSPOn;
     else if (isTargetMacOSBased() && !isMacosxVersionLT(10, 6))
       return LangOptions::SSPOn;
diff --git a/clang/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp b/clang/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp
index ce05d2d3c9058..17af1aebd6d2a 100644
--- a/clang/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/CheckSecuritySyntaxOnly.cpp
@@ -973,6 +973,8 @@ void WalkAST::checkMsg_decodeValueOfObjCType(const ObjCMessageExpr *ME) {
     if (VT < VersionTuple(11, 0))
       return;
     break;
+  case llvm::Triple::XROS:
+    break;
   default:
     return;
   }
diff --git a/clang/test/Driver/xros-driver.c b/clang/test/Driver/xros-driver.c
new file mode 100644
index 0000000000000..dd2c55ed4e70c
--- /dev/null
+++ b/clang/test/Driver/xros-driver.c
@@ -0,0 +1,41 @@
+// RUN: %clang -target arm64-apple-xros1 -c -### %s 2>&1 | FileCheck --check-prefix=VERSION1 %s
+// RUN: %clang -target arm64-apple-xros -c -### %s 2>&1 | FileCheck --check-prefix=VERSION1 %s
+
+// RUN: %clang -target arm64-apple-xros1-simulator -c -### %s 2>&1 | FileCheck --check-prefix=VERSION1_ASi %s
+
+// RUN: not %clang -target arm64-apple-xros1000 -c -### %s 2>&1 | FileCheck --check-prefix=INVALID-VERSION %s
+
+// RUN: %clang -target arm64-apple-xros1  -### %s 2>&1 | FileCheck --check-prefix=LINK %s
+// RUN: %clang -target arm64-apple-xros1-simulator  -### %s 2>&1 | FileCheck --check-prefix=LINK-SIM %s
+
+// RUN: %clang -target arm64-apple-xros1 -c -x objective-c -fobjc-arc -### %s 2>&1 | FileCheck --check-prefix=ARC %s
+// RUN: %clang -target arm64-apple-xros -c -x objective-c -fobjc-arc -### %s 2>&1 | FileCheck --check-prefix=OBJC-RUNTIME %s
+// RUN: %clang -target arm64-apple-xros2 -c -x objective-c -fobjc-arc -### %s 2>&1 | FileCheck --check-prefix=OBJC-RUNTIME2 %s
+
+// RUN: %clang -target arm64-apple-xros1 -c -x objective-c -fobjc-arc -### %s 2>&1 | FileCheck --check-prefix=ARC %s
+// RUN: %clang -target arm64-apple-xros1-simulator -c -x objective-c -fobjc-arc -### %s 2>&1 | FileCheck --check-prefix=ARC %s
+
+// RUN: %clang -target arm64-apple-xros -c -### %s 2>&1 | FileCheck --check-prefix=SSP_ON %s
+
+// RUN: %clang -target arm64e-apple-xros -c -### %s 2>&1 | FileCheck --check-prefix=CPU-ARM64E %s
+// RUN: %clang -target arm64-apple-xros -c -### %s 2>&1 | FileCheck --check-prefix=CPU-ARM64 %s
+// RUN: %clang -target arm64-apple-xros-simulator -c -### %s 2>&1 | FileCheck --check-prefix=CPU-ARM64-SIM %s
+
+// VERSION1: "-cc1"{{.*}} "-triple" "arm64-apple-xros1.0.0"
+// VERSION1_ASi: "-cc1"{{.*}} "-triple" "arm64-apple-xros1.0.0-simulator"
+// INVALID-VERSION: error: invalid version number in
+
+// VERSION1-NOT: -faligned-alloc-unavailable
+
+// LINK: "-platform_version" "xros" "1.0.0" "1.0.0"
+// LINK-SIM: "-platform_version" "xros-simulator" "1.0.0" "1.0.0"
+
+// OBJC-RUNTIME: "-fobjc-runtime=ios-17.0.0.0"
+// OBJC-RUNTIME2: "-fobjc-runtime=ios-18.0.0.0"
+// ARC-NOT: error:
+
+// SSP_ON: "-stack-protector" "1"
+
+// CPU-ARM64E: "-cc1"{{.*}} "-triple" "arm64e-apple-xros1.0.0"{{.*}} "-target-cpu" "apple-a12"{{.*}}
+// CPU-ARM64: "-cc1"{{.*}} "-triple" "arm64-apple-xros1.0.0"{{.*}} "-target-cpu" "apple-a12"
+// CPU-ARM64-SIM: "-cc1"{{.*}} "-triple" "arm64-apple-xros1.0.0-simulator"{{.*}} "-target-cpu" "apple-m1"
diff --git a/clang/test/Frontend/xros-version.c b/clang/test/Frontend/xros-version.c
new file mode 100644
index 0000000000000..68f69f3de7633
--- /dev/null
+++ b/clang/test/Frontend/xros-version.c
@@ -0,0 +1,3 @@
+// RUN: %clang_cc1 -triple arm64-apple-xros1 -dM -E -o - %s | FileCheck %s
+
+// CHECK: __ENVIRONMENT_OS_VERSION_MIN_REQUIRED__ 10000