diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -29,6 +29,7 @@
     libc.src.string.strcpy
     libc.src.string.strcspn
     libc.src.string.strlen
+    libc.src.string.strncpy
     libc.src.string.strnlen
     libc.src.string.strpbrk
     libc.src.string.strrchr
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -47,6 +47,7 @@
     libc.src.string.strcpy
     libc.src.string.strcspn
     libc.src.string.strlen
+    libc.src.string.strncpy
     libc.src.string.strnlen
     libc.src.string.strpbrk
     libc.src.string.strrchr
diff --git a/libc/src/string/CMakeLists.txt b/libc/src/string/CMakeLists.txt
--- a/libc/src/string/CMakeLists.txt
+++ b/libc/src/string/CMakeLists.txt
@@ -74,6 +74,14 @@
     strstr.h
 )
 
+add_entrypoint_object(
+  strncpy
+  SRCS
+    strncpy.cpp
+  HDRS
+    strncpy.h
+)
+
 add_entrypoint_object(
   strnlen
   SRCS
diff --git a/libc/src/string/strncpy.h b/libc/src/string/strncpy.h
new file mode 100644
--- /dev/null
+++ b/libc/src/string/strncpy.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for strncpy -----------------------*- 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_STRING_STRNCPY_H
+#define LLVM_LIBC_SRC_STRING_STRNCPY_H
+
+#include <stddef.h>
+
+namespace __llvm_libc {
+
+char *strncpy(char *__restrict dest, const char *__restrict src, size_t n);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_STRING_STRNCPY_H
diff --git a/libc/src/string/strncpy.cpp b/libc/src/string/strncpy.cpp
new file mode 100644
--- /dev/null
+++ b/libc/src/string/strncpy.cpp
@@ -0,0 +1,28 @@
+//===-- Implementation of strncpy -----------------------------------------===//
+//
+// 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/string/strncpy.h"
+
+#include "src/__support/common.h"
+#include <stddef.h> // For size_t.
+
+namespace __llvm_libc {
+
+char *LLVM_LIBC_ENTRYPOINT(strncpy)(char *__restrict dest,
+                                    const char *__restrict src, size_t n) {
+  size_t i = 0;
+  // Copy up until \0 is found.
+  for (; i < n && src[i] != '\0'; ++i)
+    dest[i] = src[i];
+  // When n>strlen(src), n-strlen(src) \0 are appended.
+  for (; i < n; ++i)
+    dest[i] = '\0';
+  return dest;
+}
+
+} // namespace __llvm_libc
diff --git a/libc/test/src/string/CMakeLists.txt b/libc/test/src/string/CMakeLists.txt
--- a/libc/test/src/string/CMakeLists.txt
+++ b/libc/test/src/string/CMakeLists.txt
@@ -72,6 +72,16 @@
     libc.src.string.strstr
 )
 
+add_libc_unittest(
+  strncpy_test
+  SUITE
+    libc_string_unittests
+  SRCS
+    strncpy_test.cpp
+  DEPENDS
+    libc.src.string.strncpy
+)
+
 add_libc_unittest(
   strnlen_test
   SUITE
diff --git a/libc/test/src/string/strncpy_test.cpp b/libc/test/src/string/strncpy_test.cpp
new file mode 100644
--- /dev/null
+++ b/libc/test/src/string/strncpy_test.cpp
@@ -0,0 +1,57 @@
+//===-- Unittests for strncpy ---------------------------------------------===//
+//
+// 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/string/strncpy.h"
+#include "utils/CPP/ArrayRef.h"
+#include "utils/UnitTest/Test.h"
+#include <stddef.h> // For size_t.
+
+class StrncpyTest : public __llvm_libc::testing::Test {
+public:
+  void check_strncpy(__llvm_libc::cpp::MutableArrayRef<char> dst,
+                     const __llvm_libc::cpp::ArrayRef<char> src, size_t n,
+                     const __llvm_libc::cpp::ArrayRef<char> expected) {
+    // Making sure we don't overflow buffer.
+    ASSERT_GE(dst.size(), n);
+    // Making sure strncpy returns dst.
+    ASSERT_EQ(__llvm_libc::strncpy(dst.data(), src.data(), n), dst.data());
+    // Expected must be of the same size as dst.
+    ASSERT_EQ(dst.size(), expected.size());
+    // Expected and dst are the same.
+    for (size_t i = 0; i < expected.size(); ++i)
+      ASSERT_EQ(expected[i], dst[i]);
+  }
+};
+
+TEST_F(StrncpyTest, Untouched) {
+  char dst[] = {'a', 'b'};
+  const char src[] = {'x', '\0'};
+  const char expected[] = {'a', 'b'};
+  check_strncpy(dst, src, 0, expected);
+}
+
+TEST_F(StrncpyTest, CopyOne) {
+  char dst[] = {'a', 'b'};
+  const char src[] = {'x', 'y'};
+  const char expected[] = {'x', 'b'}; // no \0 is appended
+  check_strncpy(dst, src, 1, expected);
+}
+
+TEST_F(StrncpyTest, CopyNull) {
+  char dst[] = {'a', 'b'};
+  const char src[] = {'\0', 'y'};
+  const char expected[] = {'\0', 'b'};
+  check_strncpy(dst, src, 1, expected);
+}
+
+TEST_F(StrncpyTest, CopyPastSrc) {
+  char dst[] = {'a', 'b'};
+  const char src[] = {'\0', 'y'};
+  const char expected[] = {'\0', '\0'};
+  check_strncpy(dst, src, 2, expected);
+}