diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
--- a/libcxx/docs/FeatureTestMacroTable.rst
+++ b/libcxx/docs/FeatureTestMacroTable.rst
@@ -234,7 +234,7 @@
     ------------------------------------------------- -----------------
     ``__cpp_lib_execution``                           *unimplemented*
     ------------------------------------------------- -----------------
-    ``__cpp_lib_format``                              *unimplemented*
+    ``__cpp_lib_format``                              ``202106L``
     ------------------------------------------------- -----------------
     ``__cpp_lib_generic_unordered_lookup``            ``201811L``
     ------------------------------------------------- -----------------
diff --git a/libcxx/include/version b/libcxx/include/version
--- a/libcxx/include/version
+++ b/libcxx/include/version
@@ -331,8 +331,8 @@
 # define __cpp_lib_erase_if                             202002L
 # undef  __cpp_lib_execution
 // # define __cpp_lib_execution                            201902L
-# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format)
-// #   define __cpp_lib_format                             202106L
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)
+#   define __cpp_lib_format                             202106L
 # endif
 # define __cpp_lib_generic_unordered_lookup             201811L
 # define __cpp_lib_int_pow2                             202002L
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/format.version.compile.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/format.version.compile.pass.cpp
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/format.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/format.version.compile.pass.cpp
@@ -44,31 +44,31 @@
 
 #elif TEST_STD_VER == 20
 
-# if !defined(_LIBCPP_VERSION)
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)
 #   ifndef __cpp_lib_format
 #     error "__cpp_lib_format should be defined in c++20"
 #   endif
 #   if __cpp_lib_format != 202106L
 #     error "__cpp_lib_format should have the value 202106L in c++20"
 #   endif
-# else // _LIBCPP_VERSION
+# else
 #   ifdef __cpp_lib_format
-#     error "__cpp_lib_format should not be defined because it is unimplemented in libc++!"
+#     error "__cpp_lib_format should not be defined when !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT) is not defined!"
 #   endif
 # endif
 
 #elif TEST_STD_VER > 20
 
-# if !defined(_LIBCPP_VERSION)
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)
 #   ifndef __cpp_lib_format
 #     error "__cpp_lib_format should be defined in c++2b"
 #   endif
 #   if __cpp_lib_format != 202106L
 #     error "__cpp_lib_format should have the value 202106L in c++2b"
 #   endif
-# else // _LIBCPP_VERSION
+# else
 #   ifdef __cpp_lib_format
-#     error "__cpp_lib_format should not be defined because it is unimplemented in libc++!"
+#     error "__cpp_lib_format should not be defined when !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT) is not defined!"
 #   endif
 # endif
 
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
@@ -2817,16 +2817,16 @@
 #   endif
 # endif
 
-# if !defined(_LIBCPP_VERSION)
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)
 #   ifndef __cpp_lib_format
 #     error "__cpp_lib_format should be defined in c++20"
 #   endif
 #   if __cpp_lib_format != 202106L
 #     error "__cpp_lib_format should have the value 202106L in c++20"
 #   endif
-# else // _LIBCPP_VERSION
+# else
 #   ifdef __cpp_lib_format
-#     error "__cpp_lib_format should not be defined because it is unimplemented in libc++!"
+#     error "__cpp_lib_format should not be defined when !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT) is not defined!"
 #   endif
 # endif
 
@@ -4054,16 +4054,16 @@
 #   endif
 # endif
 
-# if !defined(_LIBCPP_VERSION)
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)
 #   ifndef __cpp_lib_format
 #     error "__cpp_lib_format should be defined in c++2b"
 #   endif
 #   if __cpp_lib_format != 202106L
 #     error "__cpp_lib_format should have the value 202106L in c++2b"
 #   endif
-# else // _LIBCPP_VERSION
+# else
 #   ifdef __cpp_lib_format
-#     error "__cpp_lib_format should not be defined because it is unimplemented in libc++!"
+#     error "__cpp_lib_format should not be defined when !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT) is not defined!"
 #   endif
 # endif
 
diff --git a/libcxx/utils/generate_feature_test_macro_components.py b/libcxx/utils/generate_feature_test_macro_components.py
--- a/libcxx/utils/generate_feature_test_macro_components.py
+++ b/libcxx/utils/generate_feature_test_macro_components.py
@@ -311,9 +311,8 @@
     "name": "__cpp_lib_format",
     "values": { "c++20": 202106 },
     "headers": ["format"],
-    "test_suite_guard": "!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format)",
-    "libcxx_guard": "!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format)",
-    "unimplemented": True,
+    "test_suite_guard": "!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
+    "libcxx_guard": "!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
   }, {
     "name": "__cpp_lib_gcd_lcm",
     "values": { "c++17": 201606 },