Index: include/utility
===================================================================
--- include/utility
+++ include/utility
@@ -930,6 +930,12 @@
 template <class _Tp>
 using __is_inplace_type = __is_inplace_type_imp<__uncvref_t<_Tp>>;
 
+template <class _Tp> struct __is_inplace_index_imp : false_type {};
+template <size_t _Idx> struct __is_inplace_index_imp<in_place_index_t<_Idx>> : true_type {};
+
+template <class _Tp>
+using __is_inplace_index = __is_inplace_index_imp<__uncvref_t<_Tp>>;
+
 #endif // _LIBCPP_STD_VER > 14
 
 template <class _Arg, class _Result>
Index: test/libcxx/utilities/utility/__is_inplace_index.pass.cpp
===================================================================
--- /dev/null
+++ test/libcxx/utilities/utility/__is_inplace_index.pass.cpp
@@ -0,0 +1,23 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// template <class _Tp> using __is_inplace_index
+
+#include <utility>
+
+struct S {};
+
+int main() {
+  static_assert( std::__is_inplace_index<std::in_place_index_t<0>>::value, "");
+  static_assert(!std::__is_inplace_index<std::in_place_type_t<int>>::value, "");
+  static_assert(!std::__is_inplace_index<std::in_place_t>::value, "");
+  static_assert(!std::__is_inplace_index<void>::value, "");
+  static_assert(!std::__is_inplace_index<int>::value, "");
+  static_assert(!std::__is_inplace_index<S>::value, "");
+}
Index: test/libcxx/utilities/utility/__is_inplace_type.pass.cpp
===================================================================
--- /dev/null
+++ test/libcxx/utilities/utility/__is_inplace_type.pass.cpp
@@ -0,0 +1,23 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// template <class _Tp> using __is_inplace_type
+
+#include <utility>
+
+struct S {};
+
+int main() {
+  static_assert( std::__is_inplace_type<std::in_place_type_t<int>>::value, "");
+  static_assert(!std::__is_inplace_type<std::in_place_index_t<0>>::value, "");
+  static_assert(!std::__is_inplace_type<std::in_place_t>::value, "");
+  static_assert(!std::__is_inplace_type<void>::value, "");
+  static_assert(!std::__is_inplace_type<int>::value, "");
+  static_assert(!std::__is_inplace_type<S>::value, "");
+}