diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index 4824684103983..d7bdfe117d286 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -1075,6 +1075,7 @@ if(LLVM_LIBC_FULL_BUILD)
     # stdlib.h entrypoints
     libc.src.stdlib._Exit
     libc.src.stdlib.abort
+    libc.src.stdlib.abort_handler_s
     libc.src.stdlib.at_quick_exit
     libc.src.stdlib.atexit
     libc.src.stdlib.exit
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
index 5f407e842121e..9064e7df400de 100644
--- a/libc/config/linux/riscv/entrypoints.txt
+++ b/libc/config/linux/riscv/entrypoints.txt
@@ -1202,6 +1202,7 @@ if(LLVM_LIBC_FULL_BUILD)
     # stdlib.h entrypoints
     libc.src.stdlib._Exit
     libc.src.stdlib.abort
+    libc.src.stdlib.abort_handler_s
     libc.src.stdlib.at_quick_exit
     libc.src.stdlib.atexit
     libc.src.stdlib.exit
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 87b78a337b875..0c825bdb19f35 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -1241,6 +1241,7 @@ if(LLVM_LIBC_FULL_BUILD)
     # stdlib.h entrypoints
     libc.src.stdlib._Exit
     libc.src.stdlib.abort
+    libc.src.stdlib.abort_handler_s
     libc.src.stdlib.at_quick_exit
     libc.src.stdlib.atexit
     libc.src.stdlib.exit
diff --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
index b6d8b888fdffc..88ebd527a0a69 100644
--- a/libc/include/CMakeLists.txt
+++ b/libc/include/CMakeLists.txt
@@ -368,6 +368,7 @@ add_header_macro(
     .llvm-libc-types.__search_compare_t
     .llvm-libc-types.constraint_handler_t
     .llvm-libc-types.div_t
+    .llvm-libc-types.errno_t
     .llvm-libc-types.ldiv_t
     .llvm-libc-types.lldiv_t
     .llvm-libc-types.locale_t
diff --git a/libc/include/stdlib.yaml b/libc/include/stdlib.yaml
index 29fd6bc3a1e75..050cf246decf6 100644
--- a/libc/include/stdlib.yaml
+++ b/libc/include/stdlib.yaml
@@ -5,7 +5,9 @@ standards:
 merge_yaml_files:
   - stdlib-malloc.yaml
 macros:
-  - macro_name: NULL
+  - macro_name: 'LIBC_HAS_ANNEX_K'
+    macro_header: annex-k-macros.h
+  - macro_name: 'NULL'
     macro_header: null-macro.h
 types:
   - type_name: __atexithandler_t
@@ -14,6 +16,7 @@ types:
   - type_name: __search_compare_t
   - type_name: constraint_handler_t
   - type_name: div_t
+  - type_name: errno_t
   - type_name: ldiv_t
   - type_name: lldiv_t
   - type_name: locale_t
@@ -181,6 +184,15 @@ functions:
     return_type: int
     arguments:
       - type: void
+  - name: abort_handler_s
+    standards:
+      - stdc
+    return_type: void
+    arguments:
+      - type: const char *__restrict
+      - type: void *__restrict
+      - type: errno_t
+    guard: 'LIBC_HAS_ANNEX_K'
   - name: srand
     standards:
       - stdc
diff --git a/libc/src/__support/CMakeLists.txt b/libc/src/__support/CMakeLists.txt
index 0ef09a9b8c9d0..b71a56826156b 100644
--- a/libc/src/__support/CMakeLists.txt
+++ b/libc/src/__support/CMakeLists.txt
@@ -1,3 +1,4 @@
+add_subdirectory(annex_k)
 add_subdirectory(CPP)
 add_subdirectory(macros)
 
diff --git a/libc/src/__support/annex_k/CMakeLists.txt b/libc/src/__support/annex_k/CMakeLists.txt
new file mode 100644
index 0000000000000..78f5b3cddebd7
--- /dev/null
+++ b/libc/src/__support/annex_k/CMakeLists.txt
@@ -0,0 +1,12 @@
+add_header_library(
+  abort_handler_s
+  HDRS
+    abort_handler_s.h
+  DEPENDS
+    libc.hdr.stdio_macros
+    libc.hdr.types.errno_t
+    libc.src.__support.macros.config
+    libc.src.__support.macros.attributes
+    libc.src.__support.OSUtil.osutil
+    libc.src.stdlib.abort
+)
diff --git a/libc/src/__support/annex_k/abort_handler_s.h b/libc/src/__support/annex_k/abort_handler_s.h
new file mode 100644
index 0000000000000..dca3dcc2d9825
--- /dev/null
+++ b/libc/src/__support/annex_k/abort_handler_s.h
@@ -0,0 +1,43 @@
+//===-- Implementation for abort_handler_s ----------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_ANNEX_K_ABORT_HANDLER_S_H
+#define LLVM_LIBC_SRC___SUPPORT_ANNEX_K_ABORT_HANDLER_S_H
+
+#include "hdr/stdio_macros.h"
+#include "hdr/types/errno_t.h"
+#include "src/__support/OSUtil/io.h"
+#include "src/__support/common.h"
+#include "src/stdlib/abort.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace annex_k {
+
+LIBC_INLINE static void abort_handler_s(const char *__restrict msg,
+                                        [[maybe_unused]] void *__restrict ptr,
+                                        [[maybe_unused]] errno_t error) {
+  write_to_stderr("abort_handler_s was called in response to a "
+                  "runtime-constraint violation.\n\n");
+
+  if (msg)
+    write_to_stderr(msg);
+
+  write_to_stderr(
+      "\n\nNote to end users: This program was terminated as a result\
+of a bug present in the software. Please reach out to your\
+software's vendor to get more help.\n");
+
+  abort();
+}
+
+} // namespace annex_k
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_ANNEX_K_ABORT_HANDLER_S_H
diff --git a/libc/src/stdlib/CMakeLists.txt b/libc/src/stdlib/CMakeLists.txt
index c464f82dcbda7..8fd149880e2d5 100644
--- a/libc/src/stdlib/CMakeLists.txt
+++ b/libc/src/stdlib/CMakeLists.txt
@@ -647,6 +647,16 @@ add_entrypoint_object(
     .${LIBC_TARGET_OS}.abort
 )
 
+add_entrypoint_object(
+  abort_handler_s
+  SRCS
+    abort_handler_s.cpp
+  HDRS
+    abort_handler_s.h
+  DEPENDS
+    libc.src.__support.annex_k.abort_handler_s
+)
+
 add_entrypoint_object(
   system
   ALIAS
diff --git a/libc/src/stdlib/abort_handler_s.cpp b/libc/src/stdlib/abort_handler_s.cpp
new file mode 100644
index 0000000000000..85a4cd4858315
--- /dev/null
+++ b/libc/src/stdlib/abort_handler_s.cpp
@@ -0,0 +1,20 @@
+//===-- Implementation for abort_handler_s ----------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdlib/abort_handler_s.h"
+#include "src/__support/annex_k/abort_handler_s.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(void, abort_handler_s,
+                   (const char *__restrict msg, void *__restrict ptr,
+                    errno_t error)) {
+  return annex_k::abort_handler_s(msg, ptr, error);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdlib/abort_handler_s.h b/libc/src/stdlib/abort_handler_s.h
new file mode 100644
index 0000000000000..b97a081b036d2
--- /dev/null
+++ b/libc/src/stdlib/abort_handler_s.h
@@ -0,0 +1,22 @@
+//===-- Implementation header for abort_handler_s ---------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STDLIB_ABORT_HANDLER_S_H
+#define LLVM_LIBC_SRC_STDLIB_ABORT_HANDLER_S_H
+
+#include "hdr/types/errno_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+void abort_handler_s(const char *__restrict msg, void *__restrict ptr,
+                     errno_t error);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDLIB_ABORT_HANDLER_S_H