diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5930,6 +5930,10 @@
   "restrict requires a pointer or reference">;
 def err_typecheck_invalid_restrict_invalid_pointee : Error<
   "pointer to function type %0 may not be 'restrict' qualified">;
+def err_typecheck_invalid_optional_not_pointee : Error<
+  "_Optional is only valid on a pointed-to object or incomplete type (%0 is invalid)">;
+def err_typecheck_invalid_optional_not_pointee_noarg : Error<
+  "_Optional is only valid on a pointed-to object or incomplete type">;
 def ext_typecheck_zero_array_size : Extension<
   "zero size arrays are an extension">, InGroup<ZeroLengthArray>;
 def err_typecheck_zero_array_size : Error<
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -5088,6 +5088,13 @@
       Diag(DS.getRestrictSpecLoc(),
            diag::err_typecheck_invalid_restrict_not_pointer_noarg)
            << DS.getSourceRange();
+
+    // Types other than those of a pointed-to object or pointed-to incomplete
+    // type shall not be _Optional-qualified in a declaration.
+    if (TypeQuals & DeclSpec::TQ_optional)
+      Diag(DS.getOptionalSpecLoc(),
+           diag::err_typecheck_invalid_optional_not_pointee_noarg)
+          << DS.getSourceRange();
   }
 
   if (DS.isInlineSpecified())
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -5807,6 +5807,16 @@
     }
   }
 
+  // Types other than those of a pointed-to object or pointed-to incomplete type
+  // shall not be _Optional-qualified in a declaration.
+  if (T.isOptionalQualified() && !IsTypedefName &&
+      (!T->isArrayType() || !D.isPrototypeContext())) {
+    S.Diag(D.getDeclSpec().getOptionalSpecLoc(),
+           diag::err_typecheck_invalid_optional_not_pointee)
+        << T;
+    Context.getNonOptionalType(T);
+  }
+
   // Apply any undistributed attributes from the declaration or declarator.
   ParsedAttributesView NonSlidingAttrs;
   for (ParsedAttr &AL : D.getDeclarationAttributes()) {