diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -132,7 +132,8 @@
   ``[[clang::guard(nocf)]]``, which is equivalent to ``__declspec(guard(nocf))``
   when using the MSVC environment. This is to support enabling Windows Control
   Flow Guard checks with the ability to disable them for specific functions when
-  using the MinGW environment.
+  using the MinGW environment. This attribute is only available for Windows
+  targets.
 
 Windows Support
 ---------------
diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -399,6 +399,9 @@
 def TargetX86 : TargetArch<["x86"]>;
 def TargetAnyX86 : TargetArch<["x86", "x86_64"]>;
 def TargetWebAssembly : TargetArch<["wasm32", "wasm64"]>;
+def TargetHasCFGuard : TargetSpec {
+  let CustomCode = [{ Target.getTriple().isOSWindows() }];
+}
 def TargetHasDLLImportExport : TargetSpec {
   let CustomCode = [{ Target.getTriple().hasDLLImportExport() }];
 }
@@ -3494,7 +3497,7 @@
   let Documentation = [MSAllocatorDocs];
 }
 
-def CFGuard : InheritableAttr {
+def CFGuard : InheritableAttr, TargetSpecificAttr<TargetHasCFGuard> {
   // Currently only the __declspec(guard(nocf)) modifier is supported. In future
   // we might also want to support __declspec(guard(suppress)).
   let Spellings = [Declspec<"guard">, Clang<"guard">];