diff --git a/Configure b/Configure
index 32a02544b79b..bbe10a543fc7 100755
--- a/Configure
+++ b/Configure
@@ -859,6 +859,8 @@ d_statfs_f_flags=''
 d_statfs_s=''
 d_static_inline=''
 perl_static_inline=''
+d_thread_local=''
+perl_thread_local=''
 d_fstatvfs=''
 d_statvfs=''
 d_stdio_cnt_lval=''
@@ -19180,6 +19182,129 @@ eval $setvar
 $rm -f a.[co] b.[co]
 $rm_try
 
+: see what flavor, if any, of thread local storage is supported
+echo " "
+echo "Checking to see if your system supports C11 thread local storage..."
+$cat > try.c <<'EOCP'
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+
+static int plus_one = 1;
+static int minus_one = -1;
+
+PROBE_MACRO int *minion;
+
+int callback (const void *a, const void *b) {
+    int val_a = *minion * *(const int *)a;
+    int val_b = *minion * *(const int *)b;
+    return val_a < val_b ? -1 : val_a > val_b;
+}
+
+#define SIZE 8
+
+void *thread_function(void *arg) {
+    /* thread local variables should start zeroed in each thread. */
+    if (minion != NULL) {
+        fprintf(stderr, "__thread variable started with %p, should be NULL\n",
+                minion);
+        exit(2);
+    }
+    minion = &minus_one;
+
+    int array[SIZE];
+    unsigned int i;
+    for (i = 0; i < SIZE; ++i) {
+        /* "Hash randomisation" - this array isn't in sorted order: */
+        array[i ^ 5] = i * i;
+    }
+
+    qsort(array, SIZE, sizeof(int), callback);
+
+    int bad = 0;
+    for (i = 0; i < SIZE; ++i) {
+        int want = (SIZE - 1 - i) * (SIZE - 1 - i);
+        int have = array[i];
+        if (want != have) {
+            ++bad;
+            fprintf(stderr, "array[%u] - want %i, have %i\n", i, want, have);
+        }
+    }
+    if (bad)
+        exit(3);
+
+    return NULL;
+}
+
+int main(int argc, char **argv) {
+    if (minion != NULL) {
+        fprintf(stderr, "__thread variable started with %p, should be NULL\n",
+                minion);
+        exit(4);
+    }
+
+    minion = &plus_one;
+
+    pthread_t tid;
+    int result = pthread_create(&tid, NULL, thread_function, NULL);
+    if (result) {
+        fprintf(stderr, "pthread_create failed (%d)\n", result);
+        exit(5);
+    }
+
+    result = pthread_join(tid, NULL);
+    if (result) {
+        fprintf(stderr, "pthread_join failed (%d)\n", result);
+        exit(6);
+    }
+
+    if (minion == NULL) {
+        fprintf(stderr, "__thread variable should not be NULL\n");
+        exit(7);
+    }
+    if (!(minion == &plus_one && *minion == 1)) {
+        fprintf(stderr, "__thread variable should be %d @ %p, not %d @ %p\n",
+                1, &plus_one, *minion, minion);
+        exit(8);
+    }
+
+    return 0;
+}
+EOCP
+
+# Respect a hint (or previous) value for perl_thread_local, if there is one.
+case "$perl_thread_local" in
+'')	# Check the various possibilities, and break out on success.
+	for thread_local in _Thread_local __thread; do
+		set try -DPROBE_MACRO=$thread_local
+		if eval $compile && $run ./try; then
+			$echo "Your compiler supports $thread_local." >&4
+			val=$define
+			perl_thread_local="$thread_local";
+			break;
+		fi
+		$echo "Your compiler does NOT support $thread_local." >&4
+		val="$undef"
+	done
+	;;
+*thread*|*Thread*) # Some variant of thread local exists.
+	echo "Keeping your $hint value of $perl_thread_local."
+	val=$define
+	;;
+*)  # Unrecognized previous value -- blindly trust the supplied
+	# value and hope it makes sense.  Use old value for
+	# d_thread_local, if there is one.
+	echo "Keeping your $hint value of $perl_thread_local."
+	case "$d_thread_local" in
+		'') val=$define ;;
+		*)  val=$d_thread_local ;;
+	esac
+	;;
+esac
+set d_thread_local
+eval $setvar
+$rm_try
+
 : Check stream access
 $cat >&4 <<EOM
 Checking how to access stdio streams by file descriptor number...
@@ -24764,6 +24889,7 @@ d_tcsetpgrp='$d_tcsetpgrp'
 d_telldir='$d_telldir'
 d_telldirproto='$d_telldirproto'
 d_tgamma='$d_tgamma'
+d_thread_local='$d_thread_local'
 d_thread_safe_nl_langinfo_l='$d_thread_safe_nl_langinfo_l'
 d_time='$d_time'
 d_timegm='$d_timegm'
@@ -25139,6 +25265,7 @@ perl5='$perl5'
 perl='$perl'
 perl_patchlevel='$perl_patchlevel'
 perl_static_inline='$perl_static_inline'
+perl_thread_local='$perl_thread_local'
 perladmin='$perladmin'
 perllibs='$perllibs'
 perlpath='$perlpath'
diff --git a/Cross/config.sh-arm-linux b/Cross/config.sh-arm-linux
index 8c263cef4332..79a6b2c6387f 100644
--- a/Cross/config.sh-arm-linux
+++ b/Cross/config.sh-arm-linux
@@ -600,6 +600,7 @@ d_tcsetpgrp='define'
 d_telldir='define'
 d_telldirproto='define'
 d_tgamma='undef'
+d_thread_local='undef'
 d_thread_safe_nl_langinfo_l='undef'
 d_time='define'
 d_timegm='define'
@@ -967,6 +968,7 @@ perl5='/usr/bin/perl'
 perl=''
 perl_patchlevel=''
 perl_static_inline='static'
+perl_thread_local=''
 perladmin='red@criticalintegration.com'
 perllibs='-lnsl -ldl -lm -lcrypt -lutil -lc'
 perlpath='/usr/bin/perl'
diff --git a/Cross/config.sh-arm-linux-n770 b/Cross/config.sh-arm-linux-n770
index 4104807906b0..f1b7e378517e 100644
--- a/Cross/config.sh-arm-linux-n770
+++ b/Cross/config.sh-arm-linux-n770
@@ -599,6 +599,7 @@ d_tcsetpgrp='define'
 d_telldir='define'
 d_telldirproto='define'
 d_tgamma='undef'
+d_thread_local='undef'
 d_thread_safe_nl_langinfo_l='undef'
 d_time='define'
 d_timegm='define'
@@ -965,6 +966,7 @@ perl5='/usr/bin/perl'
 perl=''
 perl_patchlevel=''
 perl_static_inline='static'
+perl_thread_local=''
 perladmin='red@criticalintegration.com'
 perllibs='-lnsl -ldl -lm -lcrypt -lutil -lc'
 perlpath='/usr/bin/perl'
diff --git a/NetWare/config.wc b/NetWare/config.wc
index cd2ec7361937..bf4ad3f477da 100644
--- a/NetWare/config.wc
+++ b/NetWare/config.wc
@@ -590,6 +590,7 @@ d_tcsetpgrp='undef'
 d_telldir='define'
 d_telldirproto='define'
 d_tgamma='undef'
+d_thread_local='undef'
 d_thread_safe_nl_langinfo_l='undef'
 d_time='define'
 d_timegm='undef'
@@ -941,6 +942,7 @@ path_sep=';'
 perl5=''
 perl='perl'
 perl_static_inline='static'
+perl_thread_local=''
 perladmin=''
 perlpath='~INST_TOP~~INST_VER~\bin~INST_ARCH~\perl.nlm'
 pg=''
diff --git a/Porting/Glossary b/Porting/Glossary
index d28e8c58c8f2..0ad516532bf8 100644
--- a/Porting/Glossary
+++ b/Porting/Glossary
@@ -2763,6 +2763,10 @@ d_tgamma (d_tgamma.U):
 	indicates to the C program that the tgamma() routine is available
 	for the gamma function.  See also d_lgamma.
 
+d_thread_local (d_thread_local.U):
+	This variable conditionally defines the PERL_THREAD_LOCAL symbol. In
+	turn that gives a linkage specification for thread-local storage.
+
 d_thread_safe_nl_langinfo_l (d_nl_langinfo_l.U):
 	This variable contains the eventual value of the
 	HAS_THREAD_SAFE_NL_LANGINFO_L symbol, which indicates if the
@@ -4679,6 +4683,10 @@ PERL_SUBVERSION (Oldsyms.U):
 	development subversions.
 	This value is manually set in patchlevel.h
 
+perl_thread_local (d_thread_local.U):
+	This variable gives the value for the PERL_THREAD_LOCAL symbol (when
+	defined), which gives a linkage specification for thread-local storage.
+
 PERL_VERSION (Oldsyms.U):
 	In a Perl version number such as 5.6.2, this is the 6.
 	This value is manually set in patchlevel.h
diff --git a/Porting/config.sh b/Porting/config.sh
index 082463cda98d..be96029f7f08 100644
--- a/Porting/config.sh
+++ b/Porting/config.sh
@@ -621,6 +621,7 @@ d_tcsetpgrp='define'
 d_telldir='define'
 d_telldirproto='define'
 d_tgamma='define'
+d_thread_local='undef'
 d_thread_safe_nl_langinfo_l='define'
 d_time='define'
 d_timegm='define'
@@ -996,6 +997,7 @@ perl5='/usr/bin/perl'
 perl='perl'
 perl_patchlevel=''
 perl_static_inline='static __inline__'
+perl_thread_local=''
 perladmin='yourname@yourhost.yourplace.com'
 perllibs='-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc'
 perlpath='/opt/perl/bin/perl5.35.2'
diff --git a/config_h.SH b/config_h.SH
index 40a80e312e0f..4d3b47b6c67b 100755
--- a/config_h.SH
+++ b/config_h.SH
@@ -1073,6 +1073,18 @@ sed <<!GROK!THIS! >$CONFIG_H -e 's!^#undef\(.*/\)\*!/\*#define\1 \*!' -e 's!^#un
 #$d_static_inline HAS_STATIC_INLINE				/**/
 #define PERL_STATIC_INLINE $perl_static_inline	/**/
 
+/* PERL_THREAD_LOCAL:
+ *	This symbol, if defined, gives a linkage specification for thread-local
+ *	storage. For example, for a C11 compiler this will be _Thread_local.
+ *	Beware, some compilers are sensitive to the C language standard they are
+ *	told to parse. For example, suncc defaults to C11, so our probe will
+ *	report that _Thread_local can be used. However, if the -std=c99 is later
+ *	added to the compiler flags, then _Thread_local will become a syntax
+ *	error. Hence it is important for these flags to be consistent between
+ *	probing and use.
+ */
+#$d_thread_local PERL_THREAD_LOCAL $perl_thread_local	/**/
+
 /* USE_STDIO_PTR:
  *	This symbol is defined if the _ptr and _cnt fields (or similar)
  *	of the stdio FILE structure can be used to access the stdio buffer
diff --git a/configure.com b/configure.com
index 2704cb24595e..c53cc8f5016c 100644
--- a/configure.com
+++ b/configure.com
@@ -6554,6 +6554,7 @@ $ WC "d_statfs_f_flags='undef'"
 $ WC "d_statfs_s='undef'"
 $ WC "d_statfsflags='undef'"
 $ WC "d_static_inline='define'"
+$ WC "d_thread_local='undef'" ! see perl_thread_local
 $ WC "d_stdio_cnt_lval='" + d_stdio_cnt_lval + "'"
 $ WC "d_stdio_ptr_lval='" + d_stdio_ptr_lval + "'"
 $ WC "d_stdio_ptr_lval_nochange_cnt='" + d_stdio_ptr_lval_nochange_cnt + "'"
@@ -6886,6 +6887,7 @@ $ WC "perllibs='" + perllibs + "'"
 $ WC "perlpath='" + "''vms_prefix':[000000]Perl''exe_ext'" + "'"
 $ WC "perl_static_inline='static inline'"
 $ WC "perl_symbol='" + perl_symbol + "'"  ! VMS specific
+$ WC "perl_thread_local=''" ! FIXME - as this is ia64 ABI, it may well be supported
 $ WC "perl_verb='" + perl_verb + "'"      ! VMS specific
 $ WC "pgflquota='" + pgflquota + "'"
 $ WC "pidtype='" + pidtype + "'"
diff --git a/globals.c b/globals.c
index 045c71ca3fb9..5a78c8116698 100644
--- a/globals.c
+++ b/globals.c
@@ -30,6 +30,14 @@
  */
 #include "regcomp.h"
 
+/* We need somewhere to declare this. This file seems a good place.
+ * This is not a regular "global" in that we don't know whether it needs to
+ * exist until we include threads.h, and we don't want it as part of any
+ * global struct (if that or something similar is re-introduced. */
+
+#if defined(USE_ITHREADS) && defined(PERL_THREAD_LOCAL)
+PERL_THREAD_LOCAL void *PL_current_context;
+#endif
 
 /*
  * ex: set ts=8 sts=4 sw=4 et:
diff --git a/hints/cygwin.sh b/hints/cygwin.sh
index 20e0e5882108..40edf5f6b1cf 100644
--- a/hints/cygwin.sh
+++ b/hints/cygwin.sh
@@ -80,3 +80,9 @@ lddlflags="$lddlflags $ldflags"
 #ldflags="$ldflags -s"
 #ccdlflags="$ccdlflags -s"
 #lddlflags="$lddlflags -s"
+
+# Seems that exporting _Thread_local doesn't work on cygwin. This 6 year old
+# gcc bug suggests that maybe the problem really is binutils, but either way
+# it still doesn't work, despite our probes looking good:
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697
+d_thread_local=undef
diff --git a/hints/darwin.sh b/hints/darwin.sh
index fdfbdd4a3b94..ea521003c3b2 100644
--- a/hints/darwin.sh
+++ b/hints/darwin.sh
@@ -535,3 +535,7 @@ esac
 # mkostemp() was autodetected as present but found to not be linkable
 # on 15.6.0.  Unknown what other OS versions are affected.
 d_mkostemp=undef
+
+# Apparently the MACH-O format can't support _Thread_local in shared objects,
+# but clang isn't wise to this, so our probe works but the build fails...
+d_thread_local=undef
diff --git a/makedef.pl b/makedef.pl
index b5b07a7ecede..6f570588b321 100644
--- a/makedef.pl
+++ b/makedef.pl
@@ -189,6 +189,10 @@ BEGIN
 # All platforms export boot_DynaLoader unconditionally.
 my %export = ( boot_DynaLoader => 1 );
 
+# d_thread_local not perl_thread_local - see hints/darwin.sh
+++$export{PL_current_context}
+    if defined $Config{d_thread_local} && $define{USE_ITHREADS};
+
 sub try_symbols {
     foreach my $symbol (@_) {
 	++$export{$symbol} unless exists $skip{$symbol};
diff --git a/plan9/config_sh.sample b/plan9/config_sh.sample
index d879b3af2570..9914e86c27c0 100644
--- a/plan9/config_sh.sample
+++ b/plan9/config_sh.sample
@@ -600,6 +600,7 @@ d_tcsetpgrp='define'
 d_telldir='undef'
 d_telldirproto='undef'
 d_tgamma='undef'
+d_thread_local='undef'
 d_thread_safe_nl_langinfo_l='undef'
 d_time='define'
 d_timegm='undef'
@@ -948,6 +949,7 @@ perl5=''
 perl=''
 perl_patchlevel=''
 perl_static_inline='static'
+perl_thread_local=''
 perladmin='9trouble@plan9.bell-labs.com'
 perllibs=' '
 perlpath='/bin/perl'
diff --git a/pod/perldelta.pod b/pod/perldelta.pod
index 93dce844b2bd..392a25397528 100644
--- a/pod/perldelta.pod
+++ b/pod/perldelta.pod
@@ -89,7 +89,14 @@ There may well be none in a stable release.
 
 =item *
 
-XXX
+We now probe for compiler support for C11 thread local storage, and where
+available use this for "implicit context" for XS extensions making API calls for
+a threaded Perl build.  This requires fewer function calls at the C level than
+POSIX thread specific storage. We continue to use the the pthreads approach if
+the C11 approach is not available.
+
+F<Configure> run with the defaults will build an unthreaded Perl (which is
+slightly faster), but most operating systems ship a threaded Perl.
 
 =back
 
diff --git a/thread.h b/thread.h
index dcec0c064b84..8ec4411b0c84 100644
--- a/thread.h
+++ b/thread.h
@@ -379,19 +379,39 @@
 #    define PTHREAD_GETSPECIFIC(key) pthread_getspecific(key)
 #endif
 
-#ifndef PERL_GET_CONTEXT
-#  define PERL_GET_CONTEXT	PTHREAD_GETSPECIFIC(PL_thr_key)
-#endif
+#if defined(PERL_THREAD_LOCAL) && !defined(PERL_GET_CONTEXT) && !defined(PERL_SET_CONTEXT)
+/* Use C11 thread-local storage, where possible: */
+#  define PERL_USE_THREAD_LOCAL
+extern PERL_THREAD_LOCAL void *PL_current_context;
+
+#  define PERL_GET_CONTEXT        PL_current_context
+
+/* Set our thread-specific value anyway, in case code is reading it directly. */
+#  define PERL_SET_CONTEXT(t)                                           \
+    STMT_START {                                                        \
+        int _eC_;                                                       \
+        if ((_eC_ = pthread_setspecific(PL_thr_key, PL_current_context = (void *)(t)))) \
+            Perl_croak_nocontext("panic: pthread_setspecific (%d) [%s:%d]", \
+                                 _eC_, __FILE__, __LINE__);             \
+    } STMT_END
+
+#else
+/* else fall back to pthreads */
+
+#  ifndef PERL_GET_CONTEXT
+#    define PERL_GET_CONTEXT	PTHREAD_GETSPECIFIC(PL_thr_key)
+#  endif
 
-#ifndef PERL_SET_CONTEXT
-#  define PERL_SET_CONTEXT(t) \
+#  ifndef PERL_SET_CONTEXT
+#    define PERL_SET_CONTEXT(t) \
     STMT_START {						\
         int _eC_;						\
         if ((_eC_ = pthread_setspecific(PL_thr_key, (void *)(t))))	\
             Perl_croak_nocontext("panic: pthread_setspecific (%d) [%s:%d]",	\
                                  _eC_, __FILE__, __LINE__);	\
     } STMT_END
-#endif /* PERL_SET_CONTEXT */
+#  endif /* PERL_SET_CONTEXT */
+#endif /* PERL_THREAD_LOCAL */
 
 #ifndef INIT_THREADS
 #  ifdef NEED_PTHREAD_INIT
diff --git a/uconfig.h b/uconfig.h
index 40ca1fd42c14..a0729fab78b1 100644
--- a/uconfig.h
+++ b/uconfig.h
@@ -1038,6 +1038,18 @@
 /*#define HAS_STATIC_INLINE				/ **/
 #define PERL_STATIC_INLINE static	/**/
 
+/* PERL_THREAD_LOCAL:
+ *	This symbol, if defined, gives a linkage specification for thread-local
+ *	storage. For example, for a C11 compiler this will be _Thread_local.
+ *	Beware, some compilers are sensitive to the C language standard they are
+ *	told to parse. For example, suncc defaults to C11, so our probe will
+ *	report that _Thread_local can be used. However, if the -std=c99 is later
+ *	added to the compiler flags, then _Thread_local will become a syntax
+ *	error. Hence it is important for these flags to be consistent between
+ *	probing and use.
+ */
+/*#define PERL_THREAD_LOCAL 	/ **/
+
 /* USE_STDIO_PTR:
  *	This symbol is defined if the _ptr and _cnt fields (or similar)
  *	of the stdio FILE structure can be used to access the stdio buffer
@@ -5313,6 +5325,6 @@
 #endif
 
 /* Generated from:
- * 55a531381747550c11c2c61b9a9da2dacde4df465b874df55a9c923e495deb3a config_h.SH
- * 2fece1e405c60ae089fe55acaa42471b6fba78b7ab4cefc6d5e18a94b72fc2c4 uconfig.sh
+ * 4e866e62fb150da77cf5139ab739d14508877a3d94faa20860db45e2c62b7222 config_h.SH
+ * 088658cf942eae9136ad35b5e1a49e5387bc6a4ff80ab6b5af0b6c2c2f902e0d uconfig.sh
  * ex: set ro: */
diff --git a/uconfig.sh b/uconfig.sh
index 898ff9979fe5..7e04b1fde2db 100644
--- a/uconfig.sh
+++ b/uconfig.sh
@@ -540,6 +540,7 @@ d_tcsetpgrp='undef'
 d_telldir='undef'
 d_telldirproto='undef'
 d_tgamma='undef'
+d_thread_local='undef'
 d_thread_safe_nl_langinfo_l='undef'
 d_time='define'
 d_timegm='undef'
@@ -785,6 +786,7 @@ osvers='unknown'
 otherlibdirs=' '
 package='perl5'
 perl_static_inline='static'
+perl_thread_local=''
 phostname='hostname'
 pidtype=int
 privlib='/usr/local/lib/perl5/5.35'
diff --git a/uconfig64.sh b/uconfig64.sh
index c9a9559af7ad..1aa65fd59b52 100644
--- a/uconfig64.sh
+++ b/uconfig64.sh
@@ -540,6 +540,7 @@ d_tcsetpgrp='undef'
 d_telldir='undef'
 d_telldirproto='undef'
 d_tgamma='undef'
+d_thread_local='undef'
 d_thread_safe_nl_langinfo_l='undef'
 d_time='define'
 d_timegm='undef'
@@ -785,6 +786,7 @@ osvers='unknown'
 otherlibdirs=' '
 package='perl5'
 perl_static_inline='static'
+perl_thread_local=''
 phostname='hostname'
 pidtype=int
 privlib='/usr/local/lib/perl5/5.35'
diff --git a/win32/config.gc b/win32/config.gc
index 55280f61a1ed..d16fe3d3a19e 100644
--- a/win32/config.gc
+++ b/win32/config.gc
@@ -589,6 +589,7 @@ d_tcsetpgrp='undef'
 d_telldir='define'
 d_telldirproto='define'
 d_tgamma='define'
+d_thread_local='undef'
 d_thread_safe_nl_langinfo_l='undef'
 d_time='define'
 d_timegm='undef'
@@ -961,6 +962,7 @@ perl5=''
 perl='perl'
 perl_patchlevel='~PERL_PATCHLEVEL~'
 perl_static_inline='static __inline__'
+perl_thread_local=''
 perladmin=''
 perllibs='~libs~'
 perlpath='~INST_TOP~~INST_VER~\bin~INST_ARCH~\perl.exe'
diff --git a/win32/config.vc b/win32/config.vc
index 0f89bc6ee0eb..2f827e5a986d 100644
--- a/win32/config.vc
+++ b/win32/config.vc
@@ -589,6 +589,7 @@ d_tcsetpgrp='undef'
 d_telldir='define'
 d_telldirproto='define'
 d_tgamma='undef'
+d_thread_local='undef'
 d_thread_safe_nl_langinfo_l='undef'
 d_time='define'
 d_timegm='undef'
@@ -960,6 +961,7 @@ perl5=''
 perl='perl'
 perl_patchlevel='~PERL_PATCHLEVEL~'
 perl_static_inline='static __inline'
+perl_thread_local=''
 perladmin=''
 perllibs='~libs~'
 perlpath='~INST_TOP~~INST_VER~\bin~INST_ARCH~\perl.exe'