diff --git a/clang/include/clang/Basic/CodeGenOptions.h b/clang/include/clang/Basic/CodeGenOptions.h
--- a/clang/include/clang/Basic/CodeGenOptions.h
+++ b/clang/include/clang/Basic/CodeGenOptions.h
@@ -211,9 +211,6 @@
   /// The name of the relocation model to use.
   llvm::Reloc::Model RelocationModel;
 
-  /// The thread model to use
-  std::string ThreadModel;
-
   /// If not an empty string, trap intrinsics are lowered to calls to this
   /// function instead of to trap instructions.
   std::string TrapFuncName;
diff --git a/clang/include/clang/Basic/LangOptions.h b/clang/include/clang/Basic/LangOptions.h
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -232,6 +232,13 @@
     BKey
   };
 
+  enum class ThreadModelKind {
+    /// POSIX Threads.
+    POSIX,
+    /// Single Threaded Environment.
+    Single
+  };
+
 public:
   /// Set of enabled sanitizers.
   SanitizerSet Sanitize;
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -330,6 +330,7 @@
              "stop trivial automatic variable initialization after the specified number of instances. Must be greater than 0.")
 ENUM_LANGOPT(SignedOverflowBehavior, SignedOverflowBehaviorTy, 2, SOB_Undefined,
              "signed integer overflow handling")
+ENUM_LANGOPT(ThreadModel  , ThreadModelKind, 2, ThreadModelKind::POSIX, "Thread Model")
 
 BENIGN_LANGOPT(ArrowDepth, 32, 256,
                "maximum number of operator->s to follow")
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -453,10 +453,14 @@
                               const clang::TargetOptions &TargetOpts,
                               const LangOptions &LangOpts,
                               const HeaderSearchOptions &HSOpts) {
-  Options.ThreadModel =
-      llvm::StringSwitch<llvm::ThreadModel::Model>(CodeGenOpts.ThreadModel)
-          .Case("posix", llvm::ThreadModel::POSIX)
-          .Case("single", llvm::ThreadModel::Single);
+  switch (LangOpts.getThreadModel()) {
+  case LangOptions::ThreadModelKind::POSIX:
+    Options.ThreadModel = llvm::ThreadModel::POSIX;
+    break;
+  case LangOptions::ThreadModelKind::Single:
+    Options.ThreadModel = llvm::ThreadModel::Single;
+    break;
+  }
 
   // Set float ABI type.
   assert((CodeGenOpts.FloatABI == "soft" || CodeGenOpts.FloatABI == "softfp" ||
diff --git a/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp b/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
--- a/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
+++ b/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
@@ -49,7 +49,7 @@
   const PreprocessorOptions &PreprocessorOpts;
   CodeGenOptions CodeGenOpts;
   const TargetOptions TargetOpts;
-  const LangOptions LangOpts;
+  LangOptions LangOpts;
   std::unique_ptr<llvm::LLVMContext> VMContext;
   std::unique_ptr<llvm::Module> M;
   std::unique_ptr<CodeGen::CodeGenModule> Builder;
@@ -147,7 +147,7 @@
     // The debug info output isn't affected by CodeModel and
     // ThreadModel, but the backend expects them to be nonempty.
     CodeGenOpts.CodeModel = "default";
-    CodeGenOpts.ThreadModel = "single";
+    LangOpts.setThreadModel(LangOptions::ThreadModelKind::Single);
     CodeGenOpts.DebugTypeExtRefs = true;
     // When building a module MainFileName is the name of the modulemap file.
     CodeGenOpts.MainFileName =
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1037,12 +1037,11 @@
   Opts.StrictVTablePointers = Args.hasArg(OPT_fstrict_vtable_pointers);
   Opts.ForceEmitVTables = Args.hasArg(OPT_fforce_emit_vtables);
   Opts.UnwindTables = Args.hasArg(OPT_munwind_tables);
-  Opts.ThreadModel =
+  std::string ThreadModel =
       std::string(Args.getLastArgValue(OPT_mthread_model, "posix"));
-  if (Opts.ThreadModel != "posix" && Opts.ThreadModel != "single")
+  if (ThreadModel != "posix" && ThreadModel != "single")
     Diags.Report(diag::err_drv_invalid_value)
-        << Args.getLastArg(OPT_mthread_model)->getAsString(Args)
-        << Opts.ThreadModel;
+        << Args.getLastArg(OPT_mthread_model)->getAsString(Args) << ThreadModel;
   Opts.TrapFuncName = std::string(Args.getLastArgValue(OPT_ftrap_function_EQ));
   Opts.UseInitArray = !Args.hasArg(OPT_fno_use_init_array);
 
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -403,6 +403,12 @@
     Builder.defineMacro("__STDCPP_DEFAULT_NEW_ALIGNMENT__",
                         Twine(TI.getNewAlign() / TI.getCharWidth()) +
                             TI.getTypeConstantSuffix(TI.getSizeType()));
+
+    //   -- __STDCPP_­THREADS__
+    //      Defined, and has the value integer literal 1, if and only if a
+    //      program can have more than one thread of execution.
+    if (LangOpts.getThreadModel() == LangOptions::ThreadModelKind::POSIX)
+      Builder.defineMacro("__STDCPP_THREADS__", "1");
   }
 
   // In C11 these are environment macros. In C++11 they are only defined
diff --git a/clang/test/CXX/cpp/cpp.predefined/p2.cpp b/clang/test/CXX/cpp/cpp.predefined/p2.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/CXX/cpp/cpp.predefined/p2.cpp
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 %s -verify
+// expected-no-diagnostics
+
+#ifndef __STDCPP_THREADS__
+#error __STDCPP_THREADS__ is not defined
+#endif
diff --git a/clang/test/Preprocessor/init-aarch64.c b/clang/test/Preprocessor/init-aarch64.c
--- a/clang/test/Preprocessor/init-aarch64.c
+++ b/clang/test/Preprocessor/init-aarch64.c
@@ -233,6 +233,7 @@
 // AARCH64-NEXT: #define __SIZE_TYPE__ long unsigned int
 // AARCH64-NEXT: #define __SIZE_WIDTH__ 64
 // AARCH64_CXX: #define __STDCPP_DEFAULT_NEW_ALIGNMENT__ 16UL
+// AARCH64_CXX: #define __STDCPP_THREADS__ 1
 // AARCH64-NEXT: #define __STDC_HOSTED__ 1
 // AARCH64-NEXT: #define __STDC_UTF_16__ 1
 // AARCH64-NEXT: #define __STDC_UTF_32__ 1