diff --git a/libcxx/include/__format/format_arg.h b/libcxx/include/__format/format_arg.h
--- a/libcxx/include/__format/format_arg.h
+++ b/libcxx/include/__format/format_arg.h
@@ -14,7 +14,9 @@
 #include <__config>
 #include <__format/format_error.h>
 #include <__format/format_fwd.h>
+#include <__format/format_parse_context.h>
 #include <__functional_base>
+#include <__memory/addressof.h>
 #include <__variant/monostate.h>
 #include <string>
 #include <string_view>
@@ -57,7 +59,8 @@
   __long_double,
   __const_char_type_ptr,
   __string_view,
-  __ptr
+  __ptr,
+  __handle
 };
 } // namespace __format
 
@@ -101,6 +104,8 @@
     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__string_view);
   case __format::__arg_t::__ptr:
     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__ptr);
+  case __format::__arg_t::__handle:
+    return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__handle);
   }
   _LIBCPP_UNREACHABLE();
 }
@@ -108,8 +113,7 @@
 template <class _Context>
 class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT basic_format_arg {
 public:
-  // TODO FMT Define the handle class.
-  class handle;
+  class _LIBCPP_TEMPLATE_VIS handle;
 
   _LIBCPP_HIDE_FROM_ABI basic_format_arg() noexcept
       : __type_{__format::__arg_t::__none} {}
@@ -158,7 +162,7 @@
     const char_type* __const_char_type_ptr;
     basic_string_view<char_type> __string_view;
     const void* __ptr;
-    // TODO FMT Add the handle.
+    handle __handle;
   };
   __format::__arg_t __type_;
 
@@ -245,6 +249,34 @@
   template <class _Tp>
   requires is_void_v<_Tp> _LIBCPP_HIDE_FROM_ABI explicit basic_format_arg(_Tp* __p) noexcept
       : __ptr(__p), __type_(__format::__arg_t::__ptr) {}
+
+  template <class _Tp>
+  _LIBCPP_HIDE_FROM_ABI explicit basic_format_arg(const _Tp& __v) noexcept
+      : __handle(__v), __type_(__format::__arg_t::__handle) {}
+};
+
+template <class _Context>
+class _LIBCPP_TEMPLATE_VIS basic_format_arg<_Context>::handle {
+  friend class basic_format_arg<_Context>;
+
+public:
+  _LIBCPP_HIDE_FROM_ABI
+  void format(basic_format_parse_context<char_type>& __parse_ctx, _Context& __ctx) const {
+    __format_(__parse_ctx, __ctx, __ptr_);
+  }
+
+private:
+  const void* __ptr_;
+  void (*__format_)(basic_format_parse_context<char_type>&, _Context&, const void*);
+
+  template <class _Tp>
+  _LIBCPP_HIDE_FROM_ABI explicit handle(const _Tp& __v) noexcept
+      : __ptr_(_VSTD::addressof(__v)),
+        __format_([](basic_format_parse_context<char_type>& __parse_ctx, _Context& __ctx, const void* __ptr) {
+          typename _Context::template formatter_type<_Tp> __f;
+          __parse_ctx.advance_to(__f.parse(__parse_ctx));
+          __ctx.advance_to(__f.format(*static_cast<const _Tp*>(__ptr), __ctx));
+        }) {}
 };
 
 #endif // !defined(_LIBCPP_HAS_NO_CONCEPTS)
diff --git a/libcxx/include/format b/libcxx/include/format
--- a/libcxx/include/format
+++ b/libcxx/include/format
@@ -369,6 +369,8 @@
       [&](auto __arg) {
         if constexpr (same_as<decltype(__arg), monostate>)
           __throw_format_error("Argument index out of bounds");
+        else if constexpr (same_as<decltype(__arg), typename basic_format_arg<_Ctx>::handle>)
+          __arg.format(__parse_ctx, __ctx);
         else {
           formatter<decltype(__arg), _CharT> __formatter;
           __parse_ctx.advance_to(__formatter.parse(__parse_ctx));
diff --git a/libcxx/test/libcxx/utilities/format/format.arguments/format.arg/visit_format_arg.pass.cpp b/libcxx/test/libcxx/utilities/format/format.arguments/format.arg/visit_format_arg.pass.cpp
--- a/libcxx/test/libcxx/utilities/format/format.arguments/format.arg/visit_format_arg.pass.cpp
+++ b/libcxx/test/libcxx/utilities/format/format.arguments/format.arg/visit_format_arg.pass.cpp
@@ -8,6 +8,8 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-format
+// TODO FMT Evaluate gcc-11 status
+// UNSUPPORTED: gcc-11
 
 // This test requires the dylib support introduced in D92214.
 // XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11|12|13|14|15}}
diff --git a/libcxx/test/libcxx/utilities/format/format.arguments/format.args/get.pass.cpp b/libcxx/test/libcxx/utilities/format/format.arguments/format.args/get.pass.cpp
--- a/libcxx/test/libcxx/utilities/format/format.arguments/format.args/get.pass.cpp
+++ b/libcxx/test/libcxx/utilities/format/format.arguments/format.args/get.pass.cpp
@@ -8,6 +8,8 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-format
+// TODO FMT Evaluate gcc-11 status
+// UNSUPPORTED: gcc-11
 
 // This test requires the dylib support introduced in D92214.
 // XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11|12|13|14|15}}
diff --git a/libcxx/test/std/utilities/format/format.arguments/format.arg.store/class.pass.cpp b/libcxx/test/std/utilities/format/format.arguments/format.arg.store/class.pass.cpp
--- a/libcxx/test/std/utilities/format/format.arguments/format.arg.store/class.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.arguments/format.arg.store/class.pass.cpp
@@ -8,6 +8,8 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-format
+// TODO FMT Evaluate gcc-11 status
+// UNSUPPORTED: gcc-11
 
 // <format>
 
diff --git a/libcxx/test/std/utilities/format/format.arguments/format.arg.store/make_format_args.sh.cpp b/libcxx/test/std/utilities/format/format.arguments/format.arg.store/make_format_args.sh.cpp
--- a/libcxx/test/std/utilities/format/format.arguments/format.arg.store/make_format_args.sh.cpp
+++ b/libcxx/test/std/utilities/format/format.arguments/format.arg.store/make_format_args.sh.cpp
@@ -9,6 +9,8 @@
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-format
 // UNSUPPORTED: libcpp-has-no-wide-characters
+// TODO FMT Evaluate gcc-11 status
+// UNSUPPORTED: gcc-11
 
 // Validate it works regardless of the signedness of `char`.
 // RUN: %{cxx} %{flags} %{compile_flags} -fsigned-char -fsyntax-only %s
diff --git a/libcxx/test/std/utilities/format/format.arguments/format.arg/operator_bool.pass.cpp b/libcxx/test/std/utilities/format/format.arguments/format.arg/operator_bool.pass.cpp
--- a/libcxx/test/std/utilities/format/format.arguments/format.arg/operator_bool.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.arguments/format.arg/operator_bool.pass.cpp
@@ -8,6 +8,8 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-format
+// TODO FMT Evaluate gcc-11 status
+// UNSUPPORTED: gcc-11
 
 // <format>
 
diff --git a/libcxx/test/std/utilities/format/format.arguments/format.args/ctor.pass.cpp b/libcxx/test/std/utilities/format/format.arguments/format.args/ctor.pass.cpp
--- a/libcxx/test/std/utilities/format/format.arguments/format.args/ctor.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.arguments/format.args/ctor.pass.cpp
@@ -8,6 +8,8 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-format
+// TODO FMT Evaluate gcc-11 status
+// UNSUPPORTED: gcc-11
 
 // <format>
 
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/arg.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/arg.pass.cpp
--- a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/arg.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/arg.pass.cpp
@@ -8,6 +8,8 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-format
+// TODO FMT Evaluate gcc-11 status
+// UNSUPPORTED: gcc-11
 
 // <format>
 
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/ctor.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/ctor.pass.cpp
--- a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/ctor.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/ctor.pass.cpp
@@ -9,6 +9,8 @@
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-localization
 // UNSUPPORTED: libcpp-has-no-incomplete-format
+// TODO FMT Evaluate gcc-11 status
+// UNSUPPORTED: gcc-11
 
 // REQUIRES: locale.en_US.UTF-8
 // REQUIRES: locale.fr_FR.UTF-8
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/locale.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/locale.pass.cpp
--- a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/locale.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/locale.pass.cpp
@@ -9,6 +9,8 @@
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-localization
 // UNSUPPORTED: libcpp-has-no-incomplete-format
+// TODO FMT Evaluate gcc-11 status
+// UNSUPPORTED: gcc-11
 
 // REQUIRES: locale.en_US.UTF-8
 // REQUIRES: locale.fr_FR.UTF-8
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.handle.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.handle.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.handle.pass.cpp
@@ -0,0 +1,76 @@
+//===----------------------------------------------------------------------===//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+// UNSUPPORTED: libcpp-has-no-incomplete-format
+
+// <format>
+
+// A user defined formatter using
+// template<class Context>
+// class basic_format_arg<Context>::handle
+
+#include <format>
+
+#include <array>
+#include <cassert>
+#include <cmath>
+#include <charconv>
+#include <concepts>
+#include <string>
+#include <type_traits>
+
+#include "test_macros.h"
+
+enum class color { black, red, gold };
+const char* color_names[] = {"black", "red", "gold"};
+
+template <>
+struct std::formatter<color> : std::formatter<const char*> {
+  auto format(color c, format_context& ctx) {
+    return formatter<const char*>::format(color_names[static_cast<int>(c)], ctx);
+  }
+};
+
+void test(std::string expected, std::string_view fmt, color arg) {
+  auto parse_ctx = std::format_parse_context(fmt);
+  std::formatter<color, char> formatter;
+  static_assert(std::semiregular<decltype(formatter)>);
+
+  auto it = formatter.parse(parse_ctx);
+  assert(it == fmt.end() - (!fmt.empty() && fmt.back() == '}'));
+
+  std::string result;
+  auto out = std::back_inserter(result);
+  using FormatCtxT = std::basic_format_context<decltype(out), char>;
+
+  auto format_ctx = std::__format_context_create<decltype(out), char>(out, std::make_format_args<FormatCtxT>(arg));
+  formatter.format(arg, format_ctx);
+  assert(result == expected);
+}
+
+void test_termination_condition(std::string expected, std::string f, color arg) {
+  // The format-spec is valid if completely consumed or terminates at a '}'.
+  // The valid inputs all end with a '}'. The test is executed twice:
+  // - first with the terminating '}',
+  // - second consuming the entire input.
+  std::string_view fmt{f};
+  assert(fmt.back() == '}' && "Pre-condition failure");
+
+  test(expected, fmt, arg);
+  fmt.remove_suffix(1);
+  test(expected, fmt, arg);
+}
+
+int main(int, char**) {
+  test_termination_condition("black", "}", color::black);
+  test_termination_condition("red", "}", color::red);
+  test_termination_condition("gold", "}", color::gold);
+
+  return 0;
+}
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.char.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.char.pass.cpp
--- a/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.char.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.char.pass.cpp
@@ -8,6 +8,8 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-format
+// TODO FMT Evaluate gcc-11 status
+// UNSUPPORTED: gcc-11
 
 // <format>
 
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.signed_integral.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.signed_integral.pass.cpp
--- a/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.signed_integral.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.signed_integral.pass.cpp
@@ -8,6 +8,8 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-format
+// TODO FMT Evaluate gcc-11 status
+// UNSUPPORTED: gcc-11
 
 // <format>
 
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.unsigned_integral.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.unsigned_integral.pass.cpp
--- a/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.unsigned_integral.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.context/format.formatter.spec/formatter.unsigned_integral.pass.cpp
@@ -8,6 +8,8 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-format
+// TODO FMT Evaluate gcc-11 status
+// UNSUPPORTED: gcc-11
 
 // <format>
 
diff --git a/libcxx/test/std/utilities/format/format.functions/format_tests.h b/libcxx/test/std/utilities/format/format.functions/format_tests.h
--- a/libcxx/test/std/utilities/format/format.functions/format_tests.h
+++ b/libcxx/test/std/utilities/format/format.functions/format_tests.h
@@ -10,9 +10,12 @@
 
 #include <format>
 
-#include "make_string.h"
-
+#include <algorithm>
+#include <charconv>
 #include <cmath>
+#include <cstdint>
+
+#include "make_string.h"
 
 // In this file the following template types are used:
 // TestFunction must be callable as check(expected-result, string-to-format, args-to-format...)
@@ -39,6 +42,93 @@
 template <class T>
 using context_t = typename context<T>::type;
 
+// A user-defined type used to test the handle formatter.
+enum class status : uint16_t { foo = 0xAAAA, bar = 0x5555, foobar = 0xAA55 };
+
+// The formatter for a user-defined type used to test the handle formatter.
+template <class CharT>
+struct std::formatter<status, CharT> {
+  int type = 0;
+
+  constexpr auto parse(auto& parse_ctx) -> decltype(parse_ctx.begin()) {
+    auto begin = parse_ctx.begin();
+    auto end = parse_ctx.end();
+    if (begin == end)
+      return begin;
+
+    switch (*begin) {
+    case CharT('x'):
+      break;
+    case CharT('X'):
+      type = 1;
+      break;
+    case CharT('s'):
+      type = 2;
+      break;
+    case CharT('}'):
+      return begin;
+    default:
+      throw_format_error("The format-spec type has a type not supported for a status argument");
+    }
+
+    ++begin;
+    if (begin != end && *begin != CharT('}'))
+      throw_format_error("The format-spec should consume the input or end with a '}'");
+
+    return begin;
+  }
+
+  auto format(status s, auto& ctx) -> decltype(ctx.out()) {
+    const char* names[] = {"foo", "bar", "foobar"};
+    char buffer[6];
+    const char* begin;
+    const char* end;
+    switch (type) {
+    case 0:
+      begin = buffer;
+      buffer[0] = '0';
+      buffer[1] = 'x';
+      end = std::to_chars(&buffer[2], std::end(buffer), static_cast<uint16_t>(s), 16).ptr;
+      break;
+
+    case 1:
+      begin = buffer;
+      buffer[0] = '0';
+      buffer[1] = 'X';
+      end = std::to_chars(&buffer[2], std::end(buffer), static_cast<uint16_t>(s), 16).ptr;
+      std::transform(static_cast<const char*>(&buffer[2]), end, &buffer[2], [](char c) { return std::toupper(c); });
+      break;
+
+    case 2:
+      switch (s) {
+      case status::foo:
+        begin = names[0];
+        break;
+      case status::bar:
+        begin = names[1];
+        break;
+      case status::foobar:
+        begin = names[2];
+        break;
+      }
+      end = begin + strlen(begin);
+      break;
+    }
+
+    return std::copy(begin, end, ctx.out());
+  }
+
+private:
+  void throw_format_error(const char* s) {
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw std::format_error(s);
+#else
+    (void)s;
+    std::abort();
+#endif
+  }
+};
+
 template <class CharT>
 std::vector<std::basic_string<CharT>> invalid_types(std::string valid) {
   std::vector<std::basic_string<CharT>> result;
@@ -2505,6 +2595,29 @@
     check_exception("The format-spec type has a type not supported for a pointer argument", fmt, P(nullptr));
 }
 
+template <class CharT, class TestFunction, class ExceptionTest>
+void format_test_handle(TestFunction check, ExceptionTest check_exception) {
+  // *** Valid permuatations ***
+  check(STR("answer is '0xaaaa'"), STR("answer is '{}'"), status::foo);
+  check(STR("answer is '0xaaaa'"), STR("answer is '{:x}'"), status::foo);
+  check(STR("answer is '0XAAAA'"), STR("answer is '{:X}'"), status::foo);
+  check(STR("answer is 'foo'"), STR("answer is '{:s}'"), status::foo);
+
+  check(STR("answer is '0x5555'"), STR("answer is '{}'"), status::bar);
+  check(STR("answer is '0x5555'"), STR("answer is '{:x}'"), status::bar);
+  check(STR("answer is '0X5555'"), STR("answer is '{:X}'"), status::bar);
+  check(STR("answer is 'bar'"), STR("answer is '{:s}'"), status::bar);
+
+  check(STR("answer is '0xaa55'"), STR("answer is '{}'"), status::foobar);
+  check(STR("answer is '0xaa55'"), STR("answer is '{:x}'"), status::foobar);
+  check(STR("answer is '0XAA55'"), STR("answer is '{:X}'"), status::foobar);
+  check(STR("answer is 'foobar'"), STR("answer is '{:s}'"), status::foobar);
+
+  // *** type ***
+  for (const auto& fmt : invalid_types<CharT>("xXs"))
+    check_exception("The format-spec type has a type not supported for a status argument", fmt, status::foo);
+}
+
 template <class CharT, class TestFunction, class ExceptionTest>
 void format_test_pointer(TestFunction check, ExceptionTest check_exception) {
   format_test_pointer<std::nullptr_t, CharT>(check, check_exception);
@@ -2645,6 +2758,9 @@
   check(STR("hello 0x42"), STR("hello {}"), reinterpret_cast<void*>(0x42));
   check(STR("hello 0x42"), STR("hello {}"), reinterpret_cast<const void*>(0x42));
   format_test_pointer<CharT>(check, check_exception);
+
+  // *** Test handle formatter argument ***
+  format_test_handle<CharT>(check, check_exception);
 }
 
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS