diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index ddad083571eb1..b0a8c55835868 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -156,6 +156,12 @@ Bug Fixes to Compiler Builtins
 Bug Fixes to Attribute Support
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+Bug Fixes to C Support
+^^^^^^^^^^^^^^^^^^^^^^
+
+- No longer applying Named Return Value Optimization (NRVO) in C as it is a
+  non-conforming optimization in C. (#GH100902)
+
 Bug Fixes to C++ Support
 ^^^^^^^^^^^^^^^^^^^^^^^^
 
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 694a754646f27..0697d12d2fe0d 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -2176,7 +2176,9 @@ static void CheckPoppedLabel(LabelDecl *L, Sema &S,
 }
 
 void Sema::ActOnPopScope(SourceLocation Loc, Scope *S) {
-  S->applyNRVO();
+  // NRVO is only valid in C++, not in C.
+  if (getLangOpts().CPlusPlus)
+    S->applyNRVO();
 
   if (S->decl_empty()) return;
   assert((S->getFlags() & (Scope::DeclScope | Scope::TemplateParamScope)) &&
diff --git a/clang/test/CodeGen/nrvo.c b/clang/test/CodeGen/nrvo.c
new file mode 100644
index 0000000000000..39796ce2144e0
--- /dev/null
+++ b/clang/test/CodeGen/nrvo.c
@@ -0,0 +1,75 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 5
+// RUN: %clang_cc1 -triple i386-unknown-unknown -emit-llvm -disable-llvm-passes -o - %s | FileCheck --check-prefixes=C %s
+// RUN: %clang_cc1 -triple i386-unknown-unknown -emit-llvm -disable-llvm-passes -o - -x c++ %s | FileCheck --check-prefixes=CXX %s
+
+// NRVO is not allowed in C as it is in C++, so validate that this results in
+// use of NRVO in C++, but not in C.
+typedef struct {
+    int i, j;
+    double a, b;
+} S;
+
+int result;
+
+// C-LABEL: define dso_local void @test(
+// C-SAME: ptr dead_on_unwind noalias writable sret([[STRUCT_S:%.*]]) align 4 [[AGG_RESULT:%.*]], ptr noundef [[Q:%.*]]) #[[ATTR0:[0-9]+]] {
+// C-NEXT:  [[ENTRY:.*:]]
+// C-NEXT:    [[RESULT_PTR:%.*]] = alloca ptr, align 4
+// C-NEXT:    [[Q_ADDR:%.*]] = alloca ptr, align 4
+// C-NEXT:    [[S:%.*]] = alloca [[STRUCT_S]], align 4
+// C-NEXT:    store ptr [[AGG_RESULT]], ptr [[RESULT_PTR]], align 4
+// C-NEXT:    store ptr [[Q]], ptr [[Q_ADDR]], align 4
+// C-NEXT:    call void @llvm.memset.p0.i32(ptr align 4 [[S]], i8 0, i32 24, i1 false)
+// C-NEXT:    [[TMP0:%.*]] = load ptr, ptr [[Q_ADDR]], align 4
+// C-NEXT:    [[CMP:%.*]] = icmp eq ptr [[S]], [[TMP0]]
+// C-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+// C-NEXT:    store i32 [[CONV]], ptr @result, align 4
+// C-NEXT:    call void @llvm.memcpy.p0.p0.i32(ptr align 4 [[AGG_RESULT]], ptr align 4 [[S]], i32 24, i1 false)
+// C-NEXT:    ret void
+//
+// CXX-LABEL: define dso_local void @_Z4testP1S(
+// CXX-SAME: ptr dead_on_unwind noalias writable sret([[STRUCT_S:%.*]]) align 4 [[AGG_RESULT:%.*]], ptr noundef [[Q:%.*]]) #[[ATTR0:[0-9]+]] {
+// CXX-NEXT:  [[ENTRY:.*:]]
+// CXX-NEXT:    [[RESULT_PTR:%.*]] = alloca ptr, align 4
+// CXX-NEXT:    [[Q_ADDR:%.*]] = alloca ptr, align 4
+// CXX-NEXT:    store ptr [[AGG_RESULT]], ptr [[RESULT_PTR]], align 4
+// CXX-NEXT:    store ptr [[Q]], ptr [[Q_ADDR]], align 4
+// CXX-NEXT:    call void @llvm.memset.p0.i32(ptr align 4 [[AGG_RESULT]], i8 0, i32 24, i1 false)
+// CXX-NEXT:    [[TMP0:%.*]] = load ptr, ptr [[Q_ADDR]], align 4
+// CXX-NEXT:    [[CMP:%.*]] = icmp eq ptr [[AGG_RESULT]], [[TMP0]]
+// CXX-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+// CXX-NEXT:    store i32 [[CONV]], ptr @result, align 4
+// CXX-NEXT:    ret void
+//
+S test(S* q) {
+    S s = {0, 0, 0, 0};
+    result = &s == q;
+    return s;
+}
+
+// C-LABEL: define dso_local i32 @main(
+// C-SAME: ) #[[ATTR0]] {
+// C-NEXT:  [[ENTRY:.*:]]
+// C-NEXT:    [[RETVAL:%.*]] = alloca i32, align 4
+// C-NEXT:    [[T:%.*]] = alloca [[STRUCT_S:%.*]], align 4
+// C-NEXT:    store i32 0, ptr [[RETVAL]], align 4
+// C-NEXT:    call void @test(ptr dead_on_unwind writable sret([[STRUCT_S]]) align 4 [[T]], ptr noundef [[T]])
+// C-NEXT:    [[TMP0:%.*]] = load i32, ptr @result, align 4
+// C-NEXT:    ret i32 [[TMP0]]
+//
+// CXX-LABEL: define dso_local noundef i32 @main(
+// CXX-SAME: ) #[[ATTR2:[0-9]+]] {
+// CXX-NEXT:  [[ENTRY:.*:]]
+// CXX-NEXT:    [[RETVAL:%.*]] = alloca i32, align 4
+// CXX-NEXT:    [[T:%.*]] = alloca [[STRUCT_S:%.*]], align 4
+// CXX-NEXT:    store i32 0, ptr [[RETVAL]], align 4
+// CXX-NEXT:    call void @_Z4testP1S(ptr dead_on_unwind writable sret([[STRUCT_S]]) align 4 [[T]], ptr noundef [[T]])
+// CXX-NEXT:    [[TMP0:%.*]] = load i32, ptr @result, align 4
+// CXX-NEXT:    ret i32 [[TMP0]]
+//
+int main(void)
+{
+  S t = test(&t);
+  return result;
+}
+