diff --git a/libc/src/__support/OSUtil/darwin/CMakeLists.txt b/libc/src/__support/OSUtil/darwin/CMakeLists.txt
new file mode 100644
index 0000000000000..a3e6b93c8e992
--- /dev/null
+++ b/libc/src/__support/OSUtil/darwin/CMakeLists.txt
@@ -0,0 +1,17 @@
+if(NOT EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_ARCHITECTURE})
+  return()
+endif()
+
+add_subdirectory(${LIBC_TARGET_ARCHITECTURE})
+
+add_header_library(
+  darwin_util
+  HDRS
+    io.h
+    quick_exit.h
+    syscall.h
+  DEPENDS
+    .${LIBC_TARGET_ARCHITECTURE}.darwin_util
+    libc.src.__support.common
+    libc.src.__support.CPP.string_view
+)
diff --git a/libc/src/__support/OSUtil/darwin/arm/CMakeLists.txt b/libc/src/__support/OSUtil/darwin/arm/CMakeLists.txt
new file mode 100644
index 0000000000000..5ab95b01758c8
--- /dev/null
+++ b/libc/src/__support/OSUtil/darwin/arm/CMakeLists.txt
@@ -0,0 +1,7 @@
+add_header_library(
+  darwin_util
+  HDRS
+    syscall.h
+  DEPENDS
+    libc.src.__support.common
+)
diff --git a/libc/src/__support/OSUtil/darwin/arm/syscall.h b/libc/src/__support/OSUtil/darwin/arm/syscall.h
new file mode 100644
index 0000000000000..5b7dc7a3056ef
--- /dev/null
+++ b/libc/src/__support/OSUtil/darwin/arm/syscall.h
@@ -0,0 +1,112 @@
+//===------ inline implementation of Darwin arm64 syscalls --------* 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_OSUTIL_DARWIN_ARM_SYSCALL_H
+#define LLVM_LIBC_SRC_SUPPORT_OSUTIL_DARWIN_ARM_SYSCALL_H
+
+#include "src/__support/common.h"
+
+#define REGISTER_DECL_0                                                        \
+  register long x16 __asm__("x16") = number;                                   \
+  register long x0 __asm__("x0");
+#define REGISTER_DECL_1                                                        \
+  register long x16 __asm__("x16") = number;                                   \
+  register long x0 __asm__("x0") = arg1;
+#define REGISTER_DECL_2                                                        \
+  REGISTER_DECL_1                                                              \
+  register long x1 __asm__("x1") = arg2;
+#define REGISTER_DECL_3                                                        \
+  REGISTER_DECL_2                                                              \
+  register long x2 __asm__("x2") = arg3;
+#define REGISTER_DECL_4                                                        \
+  REGISTER_DECL_3                                                              \
+  register long x3 __asm__("x3") = arg4;
+#define REGISTER_DECL_5                                                        \
+  REGISTER_DECL_4                                                              \
+  register long x4 __asm__("x4") = arg5;
+#define REGISTER_DECL_6                                                        \
+  REGISTER_DECL_5                                                              \
+  register long x5 __asm__("x5") = arg6;
+
+#define REGISTER_CONSTRAINT_0 "r"(x16)
+#define REGISTER_CONSTRAINT_1 REGISTER_CONSTRAINT_0, "r"(x0)
+#define REGISTER_CONSTRAINT_2 REGISTER_CONSTRAINT_1, "r"(x1)
+#define REGISTER_CONSTRAINT_3 REGISTER_CONSTRAINT_2, "r"(x2)
+#define REGISTER_CONSTRAINT_4 REGISTER_CONSTRAINT_3, "r"(x3)
+#define REGISTER_CONSTRAINT_5 REGISTER_CONSTRAINT_4, "r"(x4)
+#define REGISTER_CONSTRAINT_6 REGISTER_CONSTRAINT_5, "r"(x5)
+
+#define SYSCALL_INSTR(input_constraint)                                        \
+  LIBC_INLINE_ASM("svc 0x80" : "=r"(x0) : input_constraint : "memory", "cc")
+
+namespace __llvm_libc {
+
+LIBC_INLINE long syscall_impl(long number) {
+  REGISTER_DECL_0;
+  SYSCALL_INSTR(REGISTER_CONSTRAINT_0);
+  return x0;
+}
+
+LIBC_INLINE long syscall_impl(long number, long arg1) {
+  REGISTER_DECL_1;
+  SYSCALL_INSTR(REGISTER_CONSTRAINT_1);
+  return x0;
+}
+
+LIBC_INLINE long syscall_impl(long number, long arg1, long arg2) {
+  REGISTER_DECL_2;
+  SYSCALL_INSTR(REGISTER_CONSTRAINT_2);
+  return x0;
+}
+
+LIBC_INLINE long syscall_impl(long number, long arg1, long arg2, long arg3) {
+  REGISTER_DECL_3;
+  SYSCALL_INSTR(REGISTER_CONSTRAINT_3);
+  return x0;
+}
+
+LIBC_INLINE long syscall_impl(long number, long arg1, long arg2, long arg3,
+                              long arg4) {
+  REGISTER_DECL_4;
+  SYSCALL_INSTR(REGISTER_CONSTRAINT_4);
+  return x0;
+}
+
+LIBC_INLINE long syscall_impl(long number, long arg1, long arg2, long arg3,
+                              long arg4, long arg5) {
+  REGISTER_DECL_5;
+  SYSCALL_INSTR(REGISTER_CONSTRAINT_5);
+  return x0;
+}
+
+LIBC_INLINE long syscall_impl(long number, long arg1, long arg2, long arg3,
+                              long arg4, long arg5, long arg6) {
+  REGISTER_DECL_6;
+  SYSCALL_INSTR(REGISTER_CONSTRAINT_6);
+  return x0;
+}
+
+} // namespace __llvm_libc
+
+#undef REGISTER_DECL_0
+#undef REGISTER_DECL_1
+#undef REGISTER_DECL_2
+#undef REGISTER_DECL_3
+#undef REGISTER_DECL_4
+#undef REGISTER_DECL_5
+#undef REGISTER_DECL_6
+
+#undef REGISTER_CONSTRAINT_0
+#undef REGISTER_CONSTRAINT_1
+#undef REGISTER_CONSTRAINT_2
+#undef REGISTER_CONSTRAINT_3
+#undef REGISTER_CONSTRAINT_4
+#undef REGISTER_CONSTRAINT_5
+#undef REGISTER_CONSTRAINT_6
+
+#endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_DARWIN_ARM_SYSCALL_H
diff --git a/libc/src/__support/OSUtil/darwin/io.h b/libc/src/__support/OSUtil/darwin/io.h
new file mode 100644
index 0000000000000..164d02aacc01a
--- /dev/null
+++ b/libc/src/__support/OSUtil/darwin/io.h
@@ -0,0 +1,24 @@
+//===------------- Darwin implementation of IO utils ------------*- 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_OSUTIL_DARWIN_IO_H
+#define LLVM_LIBC_SRC_SUPPORT_OSUTIL_DARWIN_IO_H
+
+#include "src/__support/CPP/string_view.h"
+#include "syscall.h" // For internal syscall function.
+
+namespace __llvm_libc {
+
+LIBC_INLINE void write_to_stderr(cpp::string_view msg) {
+  __llvm_libc::syscall_impl(4 /*SYS_write*/, 2 /* stderr */,
+                            reinterpret_cast<long>(msg.data()), msg.size());
+}
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_DARWIN_IO_H
diff --git a/libc/src/__support/OSUtil/darwin/quick_exit.h b/libc/src/__support/OSUtil/darwin/quick_exit.h
new file mode 100644
index 0000000000000..4fe5896cc812c
--- /dev/null
+++ b/libc/src/__support/OSUtil/darwin/quick_exit.h
@@ -0,0 +1,26 @@
+//===--------- Darwin implementation of a quick exit function ---*- 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_OSUTIL_DARWIN_QUICK_EXIT_H
+#define LLVM_LIBC_SRC_SUPPORT_OSUTIL_DARWIN_QUICK_EXIT_H
+
+#include "syscall.h" // For internal syscall function.
+
+#include "src/__support/common.h"
+
+namespace __llvm_libc {
+
+LIBC_INLINE void quick_exit(int status) {
+  for (;;) {
+    __llvm_libc::syscall_impl(1 /* SYS_exit */, status);
+  }
+}
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_DARWIN_QUICK_EXIT_H
diff --git a/libc/src/__support/OSUtil/darwin/syscall.h b/libc/src/__support/OSUtil/darwin/syscall.h
new file mode 100644
index 0000000000000..9ce1b3cc8459b
--- /dev/null
+++ b/libc/src/__support/OSUtil/darwin/syscall.h
@@ -0,0 +1,31 @@
+//===---------------------- Darwin syscalls ---------------------*- 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_OSUTIL_DARWIN_SYSCALL_H
+#define LLVM_LIBC_SRC_SUPPORT_OSUTIL_DARWIN_SYSCALL_H
+
+#include "src/__support/common.h"
+#include "src/__support/macros/properties/architectures.h"
+
+#ifdef LIBC_TARGET_ARCH_IS_ANY_ARM
+#include "arm/syscall.h"
+#else
+#error "Unsupported architecture"
+#endif
+
+namespace __llvm_libc {
+
+template <typename... Ts>
+LIBC_INLINE long syscall_impl(long __number, Ts... ts) {
+  static_assert(sizeof...(Ts) <= 6, "Too many arguments for syscall");
+  return syscall_impl(__number, (long)ts...);
+}
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_DARWIN_SYSCALL_H
diff --git a/libc/src/__support/OSUtil/io.h b/libc/src/__support/OSUtil/io.h
index 7727bd5d29ac8..9330ee57646de 100644
--- a/libc/src/__support/OSUtil/io.h
+++ b/libc/src/__support/OSUtil/io.h
@@ -13,6 +13,8 @@
 
 #if defined(LIBC_TARGET_ARCH_IS_GPU)
 #include "gpu/io.h"
+#elif defined(__APPLE__)
+#include "darwin/io.h"
 #elif defined(__unix__)
 #include "linux/io.h"
 #elif defined(__Fuchsia__)
diff --git a/libc/src/__support/OSUtil/quick_exit.h b/libc/src/__support/OSUtil/quick_exit.h
index 310e376f49da0..ae0192d02c1bb 100644
--- a/libc/src/__support/OSUtil/quick_exit.h
+++ b/libc/src/__support/OSUtil/quick_exit.h
@@ -13,6 +13,8 @@
 
 #if defined(LIBC_TARGET_ARCH_IS_GPU)
 #include "gpu/quick_exit.h"
+#elif defined(__APPLE__)
+#include "darwin/quick_exit.h"
 #elif defined(__unix__)
 #include "linux/quick_exit.h"
 #endif
diff --git a/libc/src/__support/OSUtil/syscall.h b/libc/src/__support/OSUtil/syscall.h
index b1137275a86f0..3601e7653123a 100644
--- a/libc/src/__support/OSUtil/syscall.h
+++ b/libc/src/__support/OSUtil/syscall.h
@@ -9,7 +9,9 @@
 #ifndef LLVM_LIBC_SRC_SUPPORT_OSUTIL_SYSCALL_H
 #define LLVM_LIBC_SRC_SUPPORT_OSUTIL_SYSCALL_H
 
-#ifdef __unix__
+#ifdef __APPLE__
+#include "darwin/syscall.h"
+#elif defined(__unix__)
 #include "linux/syscall.h"
 #endif