diff --git a/libc/src/locale/CMakeLists.txt b/libc/src/locale/CMakeLists.txt
@@ -0,0 +1,76 @@
+add_object_library(
+  locale
+  SRCS
+    locale.cpp
+  HDRS
+    locale.h
+  DEPENDS
+    libc.include.locale
+)
+
+add_entrypoint_object(
+  localeconv
+  SRCS
+    localeconv.cpp
+  HDRS
+    localeconv.h
+  DEPENDS
+    libc.include.locale
+  CXX_STANDARD
+    20 # For designated initializers
+)
+
+add_entrypoint_object(
+  newlocale
+  SRCS
+    newlocale.cpp
+  HDRS
+    newlocale.h
+  DEPENDS
+    libc.include.locale
+    .locale
+)
+
+add_entrypoint_object(
+  duplocale
+  SRCS
+    duplocale.cpp
+  HDRS
+    duplocale.h
+  DEPENDS
+    libc.include.locale
+    .locale
+)
+
+add_entrypoint_object(
+  setlocale
+  SRCS
+    setlocale.cpp
+  HDRS
+    setlocale.h
+  DEPENDS
+    libc.include.locale
+    .locale
+)
+
+add_entrypoint_object(
+  uselocale
+  SRCS
+    uselocale.cpp
+  HDRS
+    uselocale.h
+  DEPENDS
+    libc.include.locale
+    .locale
+)
+
+add_entrypoint_object(
+  freelocale
+  SRCS
+    freelocale.cpp
+  HDRS
+    freelocale.h
+  DEPENDS
+    libc.include.locale
+    .locale
+)
diff --git a/libc/src/locale/duplocale.cpp b/libc/src/locale/duplocale.cpp
@@ -0,0 +1,21 @@
+//===-- Implementation of duplocale ---------------------------------------===//
+//
+// 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/locale/duplocale.h"
+#include "include/llvm-libc-macros/locale-macros.h"
+#include "src/locale/locale.h"
+
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(locale_t, duplocale, (locale_t loc)) { return loc; }
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/locale/duplocale.h b/libc/src/locale/duplocale.h
@@ -0,0 +1,22 @@
+//===-- Implementation header for duplocale ---------------------*- 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_LOCALE_DUPLOCALE_H
+#define LLVM_LIBC_SRC_LOCALE_DUPLOCALE_H
+
+#include "src/__support/macros/config.h"
+
+#include "hdr/types/locale_t.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+locale_t duplocale(locale_t loc);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_LOCALE_DUPLOCALE_H
diff --git a/libc/src/locale/freelocale.cpp b/libc/src/locale/freelocale.cpp
@@ -0,0 +1,21 @@
+//===-- Implementation of freelocale --------------------------------------===//
+//
+// 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/locale/freelocale.h"
+#include "include/llvm-libc-macros/locale-macros.h"
+#include "src/locale/locale.h"
+
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(void, freelocale, (locale_t)) {}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/locale/freelocale.h b/libc/src/locale/freelocale.h
@@ -0,0 +1,22 @@
+//===-- Implementation header for freelocale --------------------*- 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_LOCALE_FREELOCALE_H
+#define LLVM_LIBC_SRC_LOCALE_FREELOCALE_H
+
+#include "src/__support/macros/config.h"
+
+#include "hdr/types/locale_t.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+void freelocale(locale_t loc);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_LOCALE_FREELOCALE_H
diff --git a/libc/src/locale/locale.cpp b/libc/src/locale/locale.cpp
@@ -0,0 +1,21 @@
+//===-- Implementation of locale ------------------------------------------===//
+//
+// 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/locale/locale.h"
+
+#include "include/llvm-libc-macros/locale-macros.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+__locale_t c_locale = {nullptr};
+
+locale_t locale = nullptr;
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/locale/locale.h b/libc/src/locale/locale.h
@@ -0,0 +1,36 @@
+//===-- Implementation header for the locale --------------------*- 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_LOCALE_LOCALECONV_H
+#define LLVM_LIBC_SRC_LOCALE_LOCALECONV_H
+
+#include "src/__support/macros/attributes.h"
+#include "src/__support/macros/config.h"
+
+#include "hdr/types/locale_t.h"
+
+#include <stddef.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+// We only support the "C" locale right now.
+static constexpr size_t MAX_LOCALE_NAME_SIZE = 2;
+
+struct __locale_data {
+  char name[MAX_LOCALE_NAME_SIZE];
+};
+
+// The pointer to the default "C" locale.
+extern __locale_t c_locale;
+
+// The global locale instance.
+LIBC_THREAD_LOCAL extern locale_t locale;
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_LOCALE_LOCALECONV_H
diff --git a/libc/src/locale/localeconv.cpp b/libc/src/locale/localeconv.cpp
@@ -0,0 +1,49 @@
+//===-- Implementation of localeconv --------------------------------------===//
+//
+// 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/locale/localeconv.h"
+
+#include "src/__support/CPP/limits.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+static char DOT_STRING[] = ".";
+static char EMPTY_STRING[] = "";
+
+static struct lconv C_LCONV = {
+    .decimal_point = DOT_STRING,
+    .thousands_sep = EMPTY_STRING,
+    .grouping = EMPTY_STRING,
+    .mon_decimal_point = EMPTY_STRING,
+    .mon_thousands_sep = EMPTY_STRING,
+    .mon_grouping = EMPTY_STRING,
+    .positive_sign = EMPTY_STRING,
+    .negative_sign = EMPTY_STRING,
+    .currency_symbol = EMPTY_STRING,
+    .frac_digits = CHAR_MAX,
+    .p_cs_precedes = CHAR_MAX,
+    .n_cs_precedes = CHAR_MAX,
+    .p_sep_by_space = CHAR_MAX,
+    .n_sep_by_space = CHAR_MAX,
+    .p_sign_posn = CHAR_MAX,
+    .n_sign_posn = CHAR_MAX,
+    .int_curr_symbol = EMPTY_STRING,
+    .int_frac_digits = CHAR_MAX,
+    .int_p_cs_precedes = CHAR_MAX,
+    .int_n_cs_precedes = CHAR_MAX,
+    .int_p_sep_by_space = CHAR_MAX,
+    .int_n_sep_by_space = CHAR_MAX,
+    .int_p_sign_posn = CHAR_MAX,
+    .int_n_sign_posn = CHAR_MAX,
+};
+
+LLVM_LIBC_FUNCTION(struct lconv *, localeconv, ()) { return &C_LCONV; }
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/locale/localeconv.h b/libc/src/locale/localeconv.h
@@ -0,0 +1,22 @@
+//===-- Implementation header for localeconv --------------------*- 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_LOCALE_LOCALECONV_H
+#define LLVM_LIBC_SRC_LOCALE_LOCALECONV_H
+
+#include "src/__support/macros/config.h"
+
+#include "include/llvm-libc-types/struct_lconv.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+struct lconv *localeconv();
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_LOCALE_LOCALECONV_H
diff --git a/libc/src/locale/newlocale.cpp b/libc/src/locale/newlocale.cpp
@@ -0,0 +1,28 @@
+//===-- Implementation of newlocale ---------------------------------------===//
+//
+// 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/locale/newlocale.h"
+#include "include/llvm-libc-macros/locale-macros.h"
+#include "src/locale/locale.h"
+
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(locale_t, newlocale,
+                   (int category_mask, const char *locale_name, locale_t)) {
+  cpp::string_view name(locale_name);
+  if (category_mask > LC_ALL || (!name.empty() && name != "C"))
+    return nullptr;
+
+  return &c_locale;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/locale/newlocale.h b/libc/src/locale/newlocale.h
@@ -0,0 +1,22 @@
+//===-- Implementation header for setlocale ---------------------*- 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_LOCALE_SETLOCALE_H
+#define LLVM_LIBC_SRC_LOCALE_SETLOCALE_H
+
+#include "src/__support/macros/config.h"
+
+#include "hdr/types/locale_t.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+locale_t newlocale(int category_mask, const char *locale_name, locale_t base);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_LOCALE_SETLOCALE_H
diff --git a/libc/src/locale/setlocale.cpp b/libc/src/locale/setlocale.cpp
@@ -0,0 +1,28 @@
+//===-- Implementation of setlocale ---------------------------------------===//
+//
+// 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/locale/setlocale.h"
+#include "include/llvm-libc-macros/locale-macros.h"
+#include "src/locale/locale.h"
+
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(char *, setlocale, (int category, const char *locale_name)) {
+  cpp::string_view name(locale_name);
+  if (category > LC_ALL || (!name.empty() && name != "C"))
+    return nullptr;
+
+  static char locale_str[] = "C";
+  return locale_str;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/locale/setlocale.h b/libc/src/locale/setlocale.h
@@ -0,0 +1,22 @@
+//===-- Implementation header for setlocale ---------------------*- 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_LOCALE_SETLOCALE_H
+#define LLVM_LIBC_SRC_LOCALE_SETLOCALE_H
+
+#include "src/__support/macros/config.h"
+
+#include "hdr/types/locale_t.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+char *setlocale(int category, const char *locale_name);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_LOCALE_SETLOCALE_H
diff --git a/libc/src/locale/uselocale.cpp b/libc/src/locale/uselocale.cpp
@@ -0,0 +1,23 @@
+//===-- Implementation of uselocale ---------------------------------------===//
+//
+// 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/locale/uselocale.h"
+#include "src/locale/locale.h"
+
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(locale_t, uselocale, (locale_t newloc)) {
+  if (!newloc)
+    return locale;
+  return locale = newloc;
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/locale/uselocale.h b/libc/src/locale/uselocale.h
@@ -0,0 +1,22 @@
+//===-- Implementation header for uselocale ---------------------*- 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_LOCALE_USELOCALE_H
+#define LLVM_LIBC_SRC_LOCALE_USELOCALE_H
+
+#include "src/__support/macros/config.h"
+
+#include "hdr/types/locale_t.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+locale_t uselocale(locale_t newloc);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_LOCALE_USELOCALE_H
diff --git a/libc/test/src/CMakeLists.txt b/libc/test/src/CMakeLists.txt
@@ -82,6 +82,7 @@ add_subdirectory(setjmp)
 add_subdirectory(signal)
 add_subdirectory(spawn)
 add_subdirectory(time)
+add_subdirectory(locale)
 
 if(${LIBC_TARGET_OS} STREQUAL "linux")
   add_subdirectory(pthread)

diff --git a/libc/test/src/locale/CMakeLists.txt b/libc/test/src/locale/CMakeLists.txt
@@ -0,0 +1,25 @@
+add_custom_target(libc-locale-tests)
+
+add_libc_test(
+  locale_test
+  SUITE
+    libc-locale-tests
+  SRCS
+    locale_test.cpp
+  DEPENDS
+    libc.include.locale
+    libc.src.locale.newlocale
+    libc.src.locale.uselocale
+    libc.src.locale.freelocale
+)
+
+add_libc_test(
+  localeconv_test
+  SUITE
+    libc-locale-tests
+  SRCS
+    localeconv_test.cpp
+  DEPENDS
+    libc.include.locale
+    libc.src.locale.localeconv
+)
diff --git a/libc/test/src/locale/locale_test.cpp b/libc/test/src/locale/locale_test.cpp
@@ -0,0 +1,27 @@
+//===-- Unittests for locale ----------------------------------------------===//
+//
+// 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/locale/freelocale.h"
+#include "src/locale/newlocale.h"
+#include "src/locale/uselocale.h"
+
+#include "test/UnitTest/Test.h"
+
+#include "include/llvm-libc-macros/locale-macros.h"
+
+TEST(LlvmLibcLocale, DefaultLocale) {
+  locale_t new_locale = LIBC_NAMESPACE::newlocale(LC_ALL, "C", nullptr);
+  EXPECT_NE(new_locale, static_cast<locale_t>(nullptr));
+
+  locale_t old_locale = LIBC_NAMESPACE::uselocale(new_locale);
+  EXPECT_NE(old_locale, static_cast<locale_t>(nullptr));
+
+  LIBC_NAMESPACE::freelocale(new_locale);
+
+  LIBC_NAMESPACE::uselocale(old_locale);
+}
diff --git a/libc/test/src/locale/localeconv_test.cpp b/libc/test/src/locale/localeconv_test.cpp
@@ -0,0 +1,17 @@
+//===-- Unittests for localeconv ------------------------------------------===//
+//
+// 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 "include/llvm-libc-macros/locale-macros.h"
+#include "src/locale/localeconv.h"
+
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcLocale, DefaultLocale) {
+  struct lconv *conv = LIBC_NAMESPACE::localeconv();
+  EXPECT_STREQ(conv->decimal_point, ".");
+}