diff --git a/BUILD.gn b/BUILD.gn
index 6b5b248..75fd40a 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -229,6 +229,7 @@
       "$dir_pw_status",
       "$dir_pw_stream",
       "$dir_pw_string",
+      "$dir_pw_sync",
       "$dir_pw_sys_io",
       "$dir_pw_trace",
       "$dir_pw_unit_test",
@@ -280,6 +281,7 @@
       "$dir_pw_status:tests",
       "$dir_pw_stream:tests",
       "$dir_pw_string:tests",
+      "$dir_pw_sync:tests",
       "$dir_pw_tokenizer:tests",
       "$dir_pw_trace:tests",
       "$dir_pw_trace_tokenized:tests",
diff --git a/docs/BUILD.gn b/docs/BUILD.gn
index 034587b..6f38d3c 100644
--- a/docs/BUILD.gn
+++ b/docs/BUILD.gn
@@ -94,6 +94,8 @@
     "$dir_pw_status:docs",
     "$dir_pw_stream:docs",
     "$dir_pw_string:docs",
+    "$dir_pw_sync:docs",
+    "$dir_pw_sync_stl:docs",
     "$dir_pw_sys_io:docs",
     "$dir_pw_sys_io_arduino:docs",
     "$dir_pw_sys_io_baremetal_stm32f429:docs",
diff --git a/modules.gni b/modules.gni
index e71cfb2..2576da3 100644
--- a/modules.gni
+++ b/modules.gni
@@ -66,6 +66,8 @@
   dir_pw_status = get_path_info("pw_status", "abspath")
   dir_pw_stream = get_path_info("pw_stream", "abspath")
   dir_pw_string = get_path_info("pw_string", "abspath")
+  dir_pw_sync = get_path_info("pw_sync", "abspath")
+  dir_pw_sync_stl = get_path_info("pw_sync_stl", "abspath")
   dir_pw_sys_io = get_path_info("pw_sys_io", "abspath")
   dir_pw_sys_io_baremetal_lm3s6965evb =
       get_path_info("pw_sys_io_baremetal_lm3s6965evb", "abspath")
diff --git a/pw_sync/BUILD b/pw_sync/BUILD
new file mode 100644
index 0000000..ceb60c6
--- /dev/null
+++ b/pw_sync/BUILD
@@ -0,0 +1,77 @@
+# Copyright 2020 The Pigweed Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+
+load(
+    "//pw_build:pigweed.bzl",
+    "pw_cc_library",
+    "pw_cc_test",
+)
+
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])  # Apache License 2.0
+
+# TODO(pwbug/101): Need to add support for facades/backends to Bazel.
+PW_SYNC_SPIN_LOCK_BACKEND = "//pw_sync_stl:spin_lock"
+
+pw_cc_library(
+    name = "spin_lock_facade",
+    hdrs = [
+        "public/pw_sync/spin_lock.h",
+    ],
+    includes = ["public"],
+    srcs = [
+        "spin_lock.cc"
+    ],
+    deps = [
+        PW_SYNC_SPIN_LOCK_BACKEND + "_headers",
+        "//pw_preprocessor",
+    ],
+)
+
+pw_cc_library(
+    name = "spin_lock",
+    deps = [
+        ":spin_lock_facade",
+        PW_SYNC_SPIN_LOCK_BACKEND + "_headers",
+    ],
+)
+
+pw_cc_library(
+    name = "spin_lock_backend",
+    deps = [
+       PW_SYNC_SPIN_LOCK_BACKEND,
+    ],
+)
+
+pw_cc_library(
+    name = "yield_core",
+    hdrs = [
+        "public/pw_sync/yield_core.h",
+    ],
+    includes = ["public"],
+)
+
+pw_cc_test(
+    name = "spin_lock_facade_test",
+    srcs = [
+        "spin_lock_facade_test.cc",
+        "spin_lock_facade_test_c.c",
+    ],
+    deps = [
+        ":spin_lock",
+        "//pw_preprocessor",
+        "//pw_unit_test",
+    ],
+)
diff --git a/pw_sync/BUILD.gn b/pw_sync/BUILD.gn
new file mode 100644
index 0000000..cf292b8
--- /dev/null
+++ b/pw_sync/BUILD.gn
@@ -0,0 +1,64 @@
+# Copyright 2020 The Pigweed Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+
+import("//build_overrides/pigweed.gni")
+
+import("$dir_pw_build/facade.gni")
+import("$dir_pw_build/target_types.gni")
+import("$dir_pw_docgen/docs.gni")
+import("$dir_pw_unit_test/test.gni")
+
+declare_args() {
+  # Backend for the pw_sync module's spin lock.
+  pw_sync_SPIN_LOCK_BACKEND = ""
+}
+
+config("public_include_path") {
+  include_dirs = [ "public" ]
+  visibility = [ ":*" ]
+}
+
+pw_facade("spin_lock") {
+  backend = pw_sync_SPIN_LOCK_BACKEND
+  public_configs = [ ":public_include_path" ]
+  public = [ "public/pw_sync/spin_lock.h" ]
+  public_deps = [ "$dir_pw_preprocessor" ]
+  sources = [ "spin_lock.cc" ]
+}
+
+pw_test_group("tests") {
+  tests = [ ":spin_lock_facade_test" ]
+}
+
+pw_source_set("yield_core") {
+  public = [ "public/pw_sync/yield_core.h" ]
+  public_configs = [ ":public_include_path" ]
+}
+
+pw_test("spin_lock_facade_test") {
+  enable_if = pw_sync_SPIN_LOCK_BACKEND != ""
+  sources = [
+    "spin_lock_facade_test.cc",
+    "spin_lock_facade_test_c.c",
+  ]
+  deps = [
+    ":spin_lock",
+    "$dir_pw_preprocessor",
+    pw_sync_SPIN_LOCK_BACKEND,
+  ]
+}
+
+pw_doc_group("docs") {
+  sources = [ "docs.rst" ]
+}
diff --git a/pw_sync/docs.rst b/pw_sync/docs.rst
new file mode 100644
index 0000000..1dfe23f
--- /dev/null
+++ b/pw_sync/docs.rst
@@ -0,0 +1,8 @@
+.. _module-pw_sync:
+
+-------
+pw_sync
+-------
+This is a synchronization module for Pigweed. It is not ready for use, and
+is under construction.
+
diff --git a/pw_sync/public/pw_sync/spin_lock.h b/pw_sync/public/pw_sync/spin_lock.h
new file mode 100644
index 0000000..fdce5e3
--- /dev/null
+++ b/pw_sync/public/pw_sync/spin_lock.h
@@ -0,0 +1,93 @@
+// Copyright 2020 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+#include <stdbool.h>
+
+#include "pw_preprocessor/util.h"
+
+#ifdef __cplusplus
+
+#include "pw_sync_backend/spin_lock_native.h"
+
+namespace pw::sync {
+
+// The SpinLock is a synchronization primitive that can be used to protect
+// shared data from being simultaneously accessed by multiple threads and/or
+// IRQs as a targeted global lock (except for NMIs).
+// It offers exclusive, non-recursive ownership semantics where IRQs up to a
+// backend defined level of "NMIs" will be masked to solve priority-inversion.
+//
+// NOTE: This SpinLock relies on built-in local interrupt masking to make it IRQ
+// safe without requiring the caller to mask interrupts manually when using this
+// primitive.
+//
+// Unlike global interrupt locks, this also works safely and efficiently on SMP
+// systems. This entire API is IRQ safe.
+//
+// WARNING: Code that holds a specific SpinLock must not try to re-acquire it
+// or it will deadlock. However, it is okay to nest distinct spinlocks.
+//
+// WARNING: In order to support global statically constructed SpinLocks, the
+// backend MUST ensure that any initialization required in your environment
+// prior to the creation and/or initialization of the native semaphore
+// (e.g. kernel initialization), is done before or during the invocation of the
+// global static C++ constructors.
+class SpinLock {
+ public:
+  using native_handle_type = backend::NativeSpinLockHandle;
+
+  SpinLock();
+  ~SpinLock() = default;
+  SpinLock(const SpinLock&) = delete;
+  SpinLock(SpinLock&&) = delete;
+  SpinLock& operator=(const SpinLock&) = delete;
+  SpinLock& operator=(SpinLock&&) = delete;
+
+  // Locks the spinlock, blocking indefinitely. Failures are fatal.
+  void lock();
+
+  // Attempts to lock the spinlock in a non-blocking manner.
+  // Returns true if the spinlock was successfully acquired.
+  bool try_lock();
+
+  // Unlocks the spinlock. Failures are fatal.
+  void unlock();
+
+  native_handle_type native_handle();
+
+ private:
+  // This may be a wrapper around a native type with additional members.
+  backend::NativeSpinLock native_type_;
+};
+
+}  // namespace pw::sync
+
+#include "pw_sync_backend/spin_lock_inline.h"
+
+using pw_sync_SpinLock = pw::sync::SpinLock;
+
+#else  // !defined(__cplusplus)
+
+typedef struct pw_sync_SpinLock pw_sync_SpinLock;
+
+#endif  // __cplusplus
+
+PW_EXTERN_C_START
+
+void pw_sync_SpinLock_Lock(pw_sync_SpinLock* spin_lock);
+bool pw_sync_SpinLock_TryLock(pw_sync_SpinLock* spin_lock);
+void pw_sync_SpinLock_Unlock(pw_sync_SpinLock* spin_lock);
+
+PW_EXTERN_C_END
diff --git a/pw_sync/public/pw_sync/yield_core.h b/pw_sync/public/pw_sync/yield_core.h
new file mode 100644
index 0000000..4a04e2b
--- /dev/null
+++ b/pw_sync/public/pw_sync/yield_core.h
@@ -0,0 +1,28 @@
+// Copyright 2020 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+// PW_SYNC_YIELD_CORE_FOR_SMT provides the architecture specific processor hint
+// to allow the processor to yield in the case of SMT.
+#if defined(__x86_64__) || defined(__i386__)
+#include <immintrin.h>
+#define PW_SYNC_YIELD_CORE_FOR_SMT() _mm_pause()
+
+#elif defined(__aarch64__) || defined(__arm__)
+#define PW_SYNC_YIELD_CORE_FOR_SMT() asm volatile("yield" ::: "memory")
+
+#else
+#error "No processor yield implementation for this architecture."
+
+#endif  // PW_SYNC_YIELD_CORE_FOR_SMT
diff --git a/pw_sync/spin_lock.cc b/pw_sync/spin_lock.cc
new file mode 100644
index 0000000..86de70b
--- /dev/null
+++ b/pw_sync/spin_lock.cc
@@ -0,0 +1,27 @@
+// Copyright 2020 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+#include "pw_sync/spin_lock.h"
+
+extern "C" void pw_sync_SpinLock_Lock(pw_sync_SpinLock* spin_lock) {
+  spin_lock->lock();
+}
+
+extern "C" bool pw_sync_SpinLock_TryLock(pw_sync_SpinLock* spin_lock) {
+  return spin_lock->try_lock();
+}
+
+extern "C" void pw_sync_SpinLock_Unlock(pw_sync_SpinLock* spin_lock) {
+  spin_lock->unlock();
+}
diff --git a/pw_sync/spin_lock_facade_test.cc b/pw_sync/spin_lock_facade_test.cc
new file mode 100644
index 0000000..c115bd9
--- /dev/null
+++ b/pw_sync/spin_lock_facade_test.cc
@@ -0,0 +1,67 @@
+// Copyright 2020 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+#include "gtest/gtest.h"
+#include "pw_sync/spin_lock.h"
+
+namespace pw::sync {
+namespace {
+
+extern "C" {
+
+// Functions defined in spin_lock_facade_test_c.c which call the API from C.
+void pw_sync_SpinLock_CallLock(pw_sync_SpinLock* spin_lock);
+bool pw_sync_SpinLock_CallTryLock(pw_sync_SpinLock* spin_lock);
+void pw_sync_SpinLock_CallUnlock(pw_sync_SpinLock* spin_lock);
+
+}  // extern "C"
+
+TEST(SpinLock, LockUnlock) {
+  pw::sync::SpinLock spin_lock;
+  spin_lock.lock();
+  spin_lock.unlock();
+}
+
+SpinLock static_spin_lock;
+TEST(SpinLock, LockUnlockStatic) {
+  static_spin_lock.lock();
+  // Ensure it fails to lock when already held.
+  EXPECT_FALSE(static_spin_lock.try_lock());
+  static_spin_lock.unlock();
+}
+
+TEST(SpinLock, TryLockUnlock) {
+  pw::sync::SpinLock spin_lock;
+  ASSERT_TRUE(spin_lock.try_lock());
+  // Ensure it fails to lock when already held.
+  EXPECT_FALSE(spin_lock.try_lock());
+  spin_lock.unlock();
+}
+
+TEST(SpinLock, LockUnlockInC) {
+  pw::sync::SpinLock spin_lock;
+  pw_sync_SpinLock_CallLock(&spin_lock);
+  pw_sync_SpinLock_CallUnlock(&spin_lock);
+}
+
+TEST(SpinLock, TryLockUnlockInC) {
+  pw::sync::SpinLock spin_lock;
+  ASSERT_TRUE(pw_sync_SpinLock_CallTryLock(&spin_lock));
+  // Ensure it fails to lock when already held.
+  EXPECT_FALSE(pw_sync_SpinLock_CallTryLock(&spin_lock));
+  pw_sync_SpinLock_CallUnlock(&spin_lock);
+}
+
+}  // namespace
+}  // namespace pw::sync
diff --git a/pw_sync/spin_lock_facade_test_c.c b/pw_sync/spin_lock_facade_test_c.c
new file mode 100644
index 0000000..17d0fd04
--- /dev/null
+++ b/pw_sync/spin_lock_facade_test_c.c
@@ -0,0 +1,32 @@
+// Copyright 2020 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+// These tests call the pw_sync module spin_lock API from C. The return values
+// are checked in the main C++ tests.
+
+#include <stdbool.h>
+
+#include "pw_sync/spin_lock.h"
+
+void pw_sync_SpinLock_CallLock(pw_sync_SpinLock* spin_lock) {
+  pw_sync_SpinLock_Lock(spin_lock);
+}
+
+bool pw_sync_SpinLock_CallTryLock(pw_sync_SpinLock* spin_lock) {
+  return pw_sync_SpinLock_TryLock(spin_lock);
+}
+
+void pw_sync_SpinLock_CallUnlock(pw_sync_SpinLock* spin_lock) {
+  pw_sync_SpinLock_Unlock(spin_lock);
+}
diff --git a/pw_sync_stl/BUILD b/pw_sync_stl/BUILD
new file mode 100644
index 0000000..13b6d64
--- /dev/null
+++ b/pw_sync_stl/BUILD
@@ -0,0 +1,45 @@
+# Copyright 2020 The Pigweed Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+
+load(
+    "//pw_build:pigweed.bzl",
+    "pw_cc_library",
+)
+
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])  # Apache License 2.0
+
+pw_cc_library(
+    name = "spin_lock_headers",
+    hdrs = [
+        "public/pw_sync_stl/spin_lock_inline.h",
+        "public/pw_sync_stl/spin_lock_native.h",
+        "public_overrides/pw_sync_backend/spin_lock_inline.h",
+        "public_overrides/pw_sync_backend/spin_lock_native.h",
+    ],
+    includes = [
+        "public",
+        "public_overrides",
+    ],
+)
+
+pw_cc_library(
+    name = "spin_lock",
+    deps = [
+        ":spin_lock_headers",
+        "//pw_sync:spin_lock_facade",
+        "//pw_sync:yield_core",
+    ],
+)
diff --git a/pw_sync_stl/BUILD.gn b/pw_sync_stl/BUILD.gn
new file mode 100644
index 0000000..eacd5dd
--- /dev/null
+++ b/pw_sync_stl/BUILD.gn
@@ -0,0 +1,50 @@
+# Copyright 2020 The Pigweed Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+
+import("//build_overrides/pigweed.gni")
+
+import("$dir_pw_build/target_types.gni")
+import("$dir_pw_docgen/docs.gni")
+
+config("public_include_path") {
+  include_dirs = [ "public" ]
+  visibility = [ ":*" ]
+}
+
+config("backend_config") {
+  include_dirs = [ "public_overrides" ]
+  visibility = [ ":*" ]
+}
+
+# This target provides the backend for pw::sync::SpinLock.
+pw_source_set("spin_lock_backend") {
+  public_configs = [
+    ":public_include_path",
+    ":backend_config",
+  ]
+  public = [
+    "public/pw_sync_stl/spin_lock_inline.h",
+    "public/pw_sync_stl/spin_lock_native.h",
+    "public_overrides/pw_sync_backend/spin_lock_inline.h",
+    "public_overrides/pw_sync_backend/spin_lock_native.h",
+  ]
+  public_deps = [
+    "$dir_pw_sync:spin_lock.facade",
+    "$dir_pw_sync:yield_core",
+  ]
+}
+
+pw_doc_group("docs") {
+  sources = [ "docs.rst" ]
+}
diff --git a/pw_sync_stl/docs.rst b/pw_sync_stl/docs.rst
new file mode 100644
index 0000000..5d922d2
--- /dev/null
+++ b/pw_sync_stl/docs.rst
@@ -0,0 +1,8 @@
+.. _module-pw_sync_stl:
+
+-----------
+pw_sync_stl
+-----------
+This is a set of backends for pw_sync based on the C++ STL. It is not ready for
+use, and is under construction.
+
diff --git a/pw_sync_stl/public/pw_sync_stl/spin_lock_inline.h b/pw_sync_stl/public/pw_sync_stl/spin_lock_inline.h
new file mode 100644
index 0000000..57572d0
--- /dev/null
+++ b/pw_sync_stl/public/pw_sync_stl/spin_lock_inline.h
@@ -0,0 +1,41 @@
+// Copyright 2020 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+#include "pw_sync/spin_lock.h"
+#include "pw_sync/yield_core.h"
+
+namespace pw::sync {
+
+inline SpinLock::SpinLock() : native_type_() {}
+
+inline void SpinLock::lock() {
+  while (!try_lock()) {
+    PW_SYNC_YIELD_CORE_FOR_SMT();
+  }
+}
+
+inline bool SpinLock::try_lock() {
+  return !native_type_.test_and_set(std::memory_order_acquire);
+}
+
+inline void SpinLock::unlock() {
+  native_type_.clear(std::memory_order_release);
+}
+
+inline SpinLock::native_handle_type SpinLock::native_handle() {
+  return native_type_;
+}
+
+}  // namespace pw::sync
diff --git a/pw_sync_stl/public/pw_sync_stl/spin_lock_native.h b/pw_sync_stl/public/pw_sync_stl/spin_lock_native.h
new file mode 100644
index 0000000..3358f8b
--- /dev/null
+++ b/pw_sync_stl/public/pw_sync_stl/spin_lock_native.h
@@ -0,0 +1,23 @@
+// Copyright 2020 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+#include <atomic>
+
+namespace pw::sync::backend {
+
+using NativeSpinLock = std::atomic_flag;
+using NativeSpinLockHandle = std::atomic_flag&;
+
+}  // namespace pw::sync::backend
diff --git a/pw_sync_stl/public_overrides/pw_sync_backend/spin_lock_inline.h b/pw_sync_stl/public_overrides/pw_sync_backend/spin_lock_inline.h
new file mode 100644
index 0000000..0307f88
--- /dev/null
+++ b/pw_sync_stl/public_overrides/pw_sync_backend/spin_lock_inline.h
@@ -0,0 +1,19 @@
+// Copyright 2020 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+// This override header includes the main tokenized logging header and defines
+// the PW_LOG macro as the tokenized logging macro.
+#pragma once
+
+#include "pw_sync_stl/spin_lock_inline.h"
diff --git a/pw_sync_stl/public_overrides/pw_sync_backend/spin_lock_native.h b/pw_sync_stl/public_overrides/pw_sync_backend/spin_lock_native.h
new file mode 100644
index 0000000..9d1922b
--- /dev/null
+++ b/pw_sync_stl/public_overrides/pw_sync_backend/spin_lock_native.h
@@ -0,0 +1,19 @@
+// Copyright 2020 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+// This override header includes the main tokenized logging header and defines
+// the PW_LOG macro as the tokenized logging macro.
+#pragma once
+
+#include "pw_sync_stl/spin_lock_native.h"
diff --git a/targets/host/target_toolchains.gni b/targets/host/target_toolchains.gni
index 51be296..73c61c0 100644
--- a/targets/host/target_toolchains.gni
+++ b/targets/host/target_toolchains.gni
@@ -29,6 +29,9 @@
   # Configure backend for logging facade.
   pw_log_BACKEND = "$dir_pw_log_basic"
 
+  # Configure backends for pw_sync's facades.
+  pw_sync_SPIN_LOCK_BACKEND = "$dir_pw_sync_stl:spin_lock_backend"
+
   # Configure backend for pw_sys_io facade.
   pw_sys_io_BACKEND = "$dir_pw_sys_io_stdio"