diff --git a/BUILD.gn b/BUILD.gn
index 118f4ca..6040df6 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -259,6 +259,7 @@
       "$dir_pw_hdlc:tests",
       "$dir_pw_hex_dump:tests",
       "$dir_pw_i2c:tests",
+      "$dir_pw_libc:tests",
       "$dir_pw_log:tests",
       "$dir_pw_log_multisink:tests",
       "$dir_pw_log_null:tests",
diff --git a/docs/BUILD.gn b/docs/BUILD.gn
index f0f9aa2..0c99c11 100644
--- a/docs/BUILD.gn
+++ b/docs/BUILD.gn
@@ -85,6 +85,7 @@
     "$dir_pw_interrupt:docs",
     "$dir_pw_interrupt_cortex_m:docs",
     "$dir_pw_kvs:docs",
+    "$dir_pw_libc:docs",
     "$dir_pw_log:docs",
     "$dir_pw_log_basic:docs",
     "$dir_pw_log_multisink:docs",
diff --git a/modules.gni b/modules.gni
index 05e04d5..fa5c03c 100644
--- a/modules.gni
+++ b/modules.gni
@@ -48,6 +48,7 @@
   dir_pw_interrupt = get_path_info("pw_interrupt", "abspath")
   dir_pw_interrupt_cortex_m = get_path_info("pw_interrupt_cortex_m", "abspath")
   dir_pw_kvs = get_path_info("pw_kvs", "abspath")
+  dir_pw_libc = get_path_info("pw_libc", "abspath")
   dir_pw_log = get_path_info("pw_log", "abspath")
   dir_pw_log_basic = get_path_info("pw_log_basic", "abspath")
   dir_pw_log_multisink = get_path_info("pw_log_multisink", "abspath")
diff --git a/pw_libc/BUILD b/pw_libc/BUILD
new file mode 100644
index 0000000..3131801
--- /dev/null
+++ b/pw_libc/BUILD
@@ -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.
+
+load(
+    "//pw_build:pigweed.bzl",
+    "pw_cc_test",
+)
+
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])  # Apache License 2.0
+
+pw_cc_test(
+    name = "memset_test",
+    srcs = [
+        "memset_test.cc",
+    ],
+    deps = [
+        "//pw_unit_test",
+    ],
+)
diff --git a/pw_libc/BUILD.gn b/pw_libc/BUILD.gn
new file mode 100644
index 0000000..9a55cef
--- /dev/null
+++ b/pw_libc/BUILD.gn
@@ -0,0 +1,35 @@
+# Copyright 2019 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")
+import("$dir_pw_unit_test/test.gni")
+
+config("default_config") {
+  include_dirs = [ "public" ]
+}
+
+pw_test_group("tests") {
+  tests = [ ":memset_test" ]
+}
+
+pw_test("memset_test") {
+  sources = [ "memset_test.cc" ]
+}
+
+pw_doc_group("docs") {
+  sources = [ "docs.rst" ]
+}
diff --git a/pw_libc/CMakeLists.txt b/pw_libc/CMakeLists.txt
new file mode 100644
index 0000000..0b1b28d
--- /dev/null
+++ b/pw_libc/CMakeLists.txt
@@ -0,0 +1,16 @@
+# Copyright 2020 The Pigweed Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+
+include($ENV{PW_ROOT}/pw_build/pigweed.cmake)
+
diff --git a/pw_libc/docs.rst b/pw_libc/docs.rst
new file mode 100644
index 0000000..ffee57a
--- /dev/null
+++ b/pw_libc/docs.rst
@@ -0,0 +1,8 @@
+.. _module-pw_libc:
+
+-------
+pw_libc
+-------
+The ``pw_libc`` module provides a restricted subset of libc suitable for some
+microcontroller projects. At this time, only a test suite is provided for
+certain libc functions.
diff --git a/pw_libc/memset_test.cc b/pw_libc/memset_test.cc
new file mode 100644
index 0000000..5ab2a3f
--- /dev/null
+++ b/pw_libc/memset_test.cc
@@ -0,0 +1,115 @@
+// 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 tests the system installed C standard library version of memset.
+//
+// Note: We have caught real production bugs with these tests. Do not assume
+// your vendor's C library is correct! For standard C functions like memset and
+// memcpy, there are compiler intrisics which assume that the C standard is
+// followed. If the implemention of memset or memcpy does not exactly follow
+// the standard, subtle and hard to track down bugs can be the result.
+
+#include <array>
+#include <cstring>
+#include <numeric>
+
+#include "gtest/gtest.h"
+
+namespace pw {
+namespace {
+
+// From the ISO C standard:
+// http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf
+//
+// Section 7.21.6.1: memset(void *s, int c, size_t n)
+//
+//   void* memset(void* buffer,
+//                int character,
+//                size_t num_bytes);
+//
+//   Copy c into the first n bytes of s.
+//   Returns buffer, a copy of the destination pointer.
+//
+
+TEST(Memset, EmptyCase) {
+  std::array<char, 5> arr{'h', 'e', 'l', 'l', 'o'};
+  void* ret = memset(arr.data(), 0, 0);
+
+  // Destination buffer returned.
+  EXPECT_EQ(ret, arr.data());
+
+  // Destination buffer untouched.
+  constexpr std::array<char, 5> kExpected{'h', 'e', 'l', 'l', 'o'};
+  EXPECT_TRUE(
+      std::equal(arr.begin(), arr.end(), kExpected.begin(), kExpected.end()));
+}
+
+TEST(Memset, OneCharacter) {
+  std::array<char, 5> arr{'h', 'e', 'l', 'l', 'o'};
+  void* ret = memset(arr.data(), 0, 1);
+
+  // Ensure the destination buffer is returned.
+  EXPECT_EQ(ret, arr.data());
+
+  // Ensure the destination buffer is untouched.
+  constexpr std::array<char, 5> kExpected{0, 'e', 'l', 'l', 'o'};
+  EXPECT_TRUE(
+      std::equal(arr.begin(), arr.end(), kExpected.begin(), kExpected.end()));
+}
+
+// Now do a detailed case with more values. Span both word sizes and alignments
+// to ensure we hit some edge cases.
+TEST(Memset, MultipleSizesMultipleAlignments) {
+  constexpr int kMaxBytes = 64;
+  std::array<char, kMaxBytes> arr;
+
+  constexpr int kMaxAlignment = 16;
+
+  // Avoid 0 sentinel to prevent interaction with uninitialized memory.
+  constexpr char kSentinel = 3;
+  constexpr char kIotaStart = kSentinel + 7;
+
+  // Try different alignments.
+  for (int alignment = 0; alignment < kMaxAlignment; ++alignment) {
+    // Try different memset sizes.
+    for (int write_size = 0; write_size < (kMaxBytes - kMaxAlignment);
+         ++write_size) {
+      // Fill entire array with incrementing integers; starting above sentinel.
+      std::iota(arr.begin(), arr.end(), kIotaStart);
+
+      // Memset the first write_size bytes, with our sentinel
+      void* write_head = &arr[alignment];
+      const void* ret = memset(write_head, kSentinel, write_size);
+
+      // Check destination buffer returned.
+      EXPECT_EQ(ret, write_head);
+
+      for (int j = 0; j < kMaxBytes; ++j) {
+        if (j < alignment) {
+          // First part of destination buffer untouched; should match iota.
+          EXPECT_EQ(arr[j], kIotaStart + j);
+        } else if (j < alignment + write_size) {
+          // Second part is set to the sentinel value.
+          EXPECT_EQ(arr[j], kSentinel);
+        } else {
+          // Third part is back to the iota content.
+          EXPECT_EQ(arr[j], kIotaStart + j);
+        }
+      }
+    }
+  }
+}
+
+}  // namespace
+}  // namespace pw