diff --git a/clang/lib/Basic/Targets/OSTargets.cpp b/clang/lib/Basic/Targets/OSTargets.cpp
--- a/clang/lib/Basic/Targets/OSTargets.cpp
+++ b/clang/lib/Basic/Targets/OSTargets.cpp
@@ -203,6 +203,7 @@
   }
 
   Builder.defineMacro("_INTEGRAL_MAX_BITS", "64");
+  Builder.defineMacro("__STDC_NO_THREADS__");
 
   // Starting with VS 2022 17.1, MSVC predefines the below macro to inform
   // users of the execution character set defined at compile time.
diff --git a/clang/test/Preprocessor/init.c b/clang/test/Preprocessor/init.c
--- a/clang/test/Preprocessor/init.c
+++ b/clang/test/Preprocessor/init.c
@@ -195,6 +195,7 @@
 // MSEXT-NOT:#define _NATIVE_WCHAR_T_DEFINED 1
 // MSEXT-NOT:#define _WCHAR_T_DEFINED 1
 // MSEXT:#define _MSVC_EXECUTION_CHARACTER_SET 65001
+// MSEXT:#define __STDC_NO_THREADS__ 1
 //
 //
 // RUN: %clang_cc1 -x c++ -fms-extensions -triple i686-pc-win32 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix MSEXT-CXX %s