diff --git a/NEWS b/NEWS
index 2fe0396b2d..1d048de0e6 100644
--- a/NEWS
+++ b/NEWS
@@ -31,6 +31,13 @@ Major new features:
 * The iconv program now supports converting files in place.  The program
   automatically uses a temporary file if required.
 
+* The GNU C Library now supports a feature test macro _ISOC2Y_SOURCE to
+  enable features from the draft ISO C2Y standard.  Only some features from
+  this draft standard are supported by the GNU C Library, and as the draft
+  is under active development, the set of features enabled by this macro is
+  liable to change.  Features from C2Y are also enabled by _GNU_SOURCE, or
+  by compiling with "gcc -std=gnu2y".
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * The big-endian ARC port (arceb-linux-gnu) has been removed.
diff --git a/include/features.h b/include/features.h
index 093de6f44c..0a8aa7c4f9 100644
--- a/include/features.h
+++ b/include/features.h
@@ -26,6 +26,7 @@
    _ISOC11_SOURCE	Extensions to ISO C99 from ISO C11.
    _ISOC23_SOURCE	Extensions to ISO C99 from ISO C23.
    _ISOC2X_SOURCE	Old name for _ISOC23_SOURCE.
+   _ISOC2Y_SOURCE	Extensions to ISO C23 from ISO C2Y.
    __STDC_WANT_LIB_EXT2__
 			Extensions to ISO C99 from TR 27431-2:2010.
    __STDC_WANT_IEC_60559_BFP_EXT__
@@ -150,6 +151,7 @@
 #undef	__USE_FORTIFY_LEVEL
 #undef	__KERNEL_STRICT_NAMES
 #undef	__GLIBC_USE_ISOC23
+#undef	__GLIBC_USE_ISOC2Y
 #undef	__GLIBC_USE_DEPRECATED_GETS
 #undef	__GLIBC_USE_DEPRECATED_SCANF
 #undef	__GLIBC_USE_C23_STRTOL
@@ -216,6 +218,8 @@
 # define _ISOC11_SOURCE	1
 # undef  _ISOC23_SOURCE
 # define _ISOC23_SOURCE	1
+# undef  _ISOC2Y_SOURCE
+# define _ISOC2Y_SOURCE	1
 # undef  _POSIX_SOURCE
 # define _POSIX_SOURCE	1
 # undef  _POSIX_C_SOURCE
@@ -239,15 +243,23 @@
 #if (defined _DEFAULT_SOURCE					\
      || (!defined __STRICT_ANSI__				\
 	 && !defined _ISOC99_SOURCE && !defined _ISOC11_SOURCE	\
-	 && !defined _ISOC23_SOURCE				\
+	 && !defined _ISOC23_SOURCE && !defined _ISOC2Y_SOURCE	\
 	 && !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE	\
 	 && !defined _XOPEN_SOURCE))
 # undef  _DEFAULT_SOURCE
 # define _DEFAULT_SOURCE	1
 #endif
 
+/* This is to enable the ISO C2Y extension.  */
+#if (defined _ISOC2Y_SOURCE \
+     || (defined __STDC_VERSION__ && __STDC_VERSION__ > 202311L))
+# define __GLIBC_USE_ISOC2Y	1
+#else
+# define __GLIBC_USE_ISOC2Y	0
+#endif
+
 /* This is to enable the ISO C23 extension.  */
-#if (defined _ISOC23_SOURCE \
+#if (defined _ISOC23_SOURCE || defined _ISOC2Y_SOURCE \
      || (defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L))
 # define __GLIBC_USE_ISOC23	1
 #else
@@ -255,21 +267,22 @@
 #endif
 
 /* This is to enable the ISO C11 extension.  */
-#if (defined _ISOC11_SOURCE || defined _ISOC23_SOURCE \
+#if (defined _ISOC11_SOURCE || defined _ISOC23_SOURCE	\
+     || defined _ISOC2Y_SOURCE				\
      || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 201112L))
 # define __USE_ISOC11	1
 #endif
 
 /* This is to enable the ISO C99 extension.  */
 #if (defined _ISOC99_SOURCE || defined _ISOC11_SOURCE			\
-     || defined _ISOC23_SOURCE						\
+     || defined _ISOC23_SOURCE || defined _ISOC2Y_SOURCE		\
      || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L))
 # define __USE_ISOC99	1
 #endif
 
 /* This is to enable the ISO C90 Amendment 1:1995 extension.  */
 #if (defined _ISOC99_SOURCE || defined _ISOC11_SOURCE			\
-     || defined _ISOC23_SOURCE						\
+     || defined _ISOC23_SOURCE || defined _ISOC2Y_SOURCE		\
      || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199409L))
 # define __USE_ISOC95	1
 #endif
diff --git a/manual/creature.texi b/manual/creature.texi
index be0a5ac7e6..09e1c9670f 100644
--- a/manual/creature.texi
+++ b/manual/creature.texi
@@ -233,6 +233,13 @@ Only some features from this draft standard are supported by
 @theglibc{}.  The older name @code{_ISOC2X_SOURCE} is also supported.
 @end defvr
 
+@defvr Macro _ISOC2Y_SOURCE
+@standards{C2Y, (none)}
+If this macro is defined, ISO C2Y extensions to ISO C23 are included.
+Only some features from this draft standard are supported by
+@theglibc{}.
+@end defvr
+
 @defvr Macro __STDC_WANT_LIB_EXT2__
 @standards{ISO, (none)}
 If you define this macro to the value @code{1}, features from ISO/IEC