diff --git a/libc/src/__support/File/linux_dir.cpp b/libc/src/__support/File/linux_dir.cpp
@@ -0,0 +1,56 @@
+//===--- Linux implementation of the Dir helpers --------------------------===//
+//
+// 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 "dir.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+
+#include <errno.h>
+#include <fcntl.h>       // For open flags
+#include <sys/syscall.h> // For syscall numbers
+
+namespace __llvm_libc {
+
+int platform_opendir(const char *name) {
+  int open_flags = O_RDONLY | O_DIRECTORY | O_CLOEXEC;
+#ifdef SYS_open
+  int fd = __llvm_libc::syscall(SYS_open, name, open_flags);
+#elif defined(SYS_openat)
+  int fd = __llvm_libc::syscall(SYS_openat, AT_FDCWD, name, open_flags);
+#else
+#error                                                                         \
+    "SYS_open and SYS_openat syscalls not available to perform an open operation."
+#endif
+
+  if (fd < 0) {
+    errno = -fd;
+    return -1;
+  }
+  return fd;
+}
+
+size_t platform_fetch_dirents(int fd, cpp::MutableArrayRef<uint8_t> buffer) {
+  long size =
+      __llvm_libc::syscall(SYS_getdents, fd, buffer.data(), buffer.size());
+  if (size < 0) {
+    errno = -size;
+    return 0;
+  }
+  return size;
+}
+
+bool platform_closedir(int fd) {
+  long ret = __llvm_libc::syscall(SYS_close, fd);
+  if (ret < 0) {
+    errno = -ret;
+    return false;
+  }
+  return true;
+}
+
+} // namespace __llvm_libc
diff --git a/libc/src/dirent/CMakeLists.txt b/libc/src/dirent/CMakeLists.txt
@@ -0,0 +1,47 @@
+add_entrypoint_object(
+  opendir
+  SRCS
+    opendir.cpp
+  HDRS
+    opendir.h
+  DEPENDS
+    libc.include.dirent
+    libc.src.__support.File.dir
+    libc.src.__support.File.platform_dir
+)
+
+add_entrypoint_object(
+  dirfd
+  SRCS
+    dirfd.cpp
+  HDRS
+    dirfd.h
+  DEPENDS
+    libc.include.dirent
+    libc.src.__support.File.dir
+    libc.src.__support.File.platform_dir
+)
+
+add_entrypoint_object(
+  closedir
+  SRCS
+    closedir.cpp
+  HDRS
+    closedir.h
+  DEPENDS
+    libc.include.dirent
+    libc.src.__support.File.dir
+    libc.src.__support.File.platform_dir
+)
+
+add_entrypoint_object(
+  readdir
+  SRCS
+    readdir.cpp
+  HDRS
+    readdir.h
+  DEPENDS
+    libc.include.dirent
+    libc.src.__support.File.dir
+    libc.src.__support.File.platform_dir
+)
diff --git a/libc/src/dirent/closedir.cpp b/libc/src/dirent/closedir.cpp
@@ -0,0 +1,23 @@
+//===-- Implementation of closedir ----------------------------------------===//
+//
+// 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 "closedir.h"
+
+#include "src/__support/File/dir.h"
+#include "src/__support/common.h"
+
+#include <dirent.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, closedir, (::DIR * dir)) {
+  auto *d = reinterpret_cast<__llvm_libc::Dir *>(dir);
+  return d->close();
+}
+
+} // namespace __llvm_libc
diff --git a/libc/src/dirent/closedir.h b/libc/src/dirent/closedir.h
@@ -0,0 +1,20 @@
+//===-- Implementation header of closedir -----------------------*- 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_DIRENT_CLOSEDIR_H
+#define LLVM_LIBC_SRC_DIRENT_CLOSEDIR_H
+
+#include <dirent.h>
+
+namespace __llvm_libc {
+
+int closedir(::DIR *dir);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_DIRENT_CLOSEDIR_H
diff --git a/libc/src/dirent/dirfd.cpp b/libc/src/dirent/dirfd.cpp
@@ -0,0 +1,23 @@
+//===-- Implementation of dirfd -------------------------------------------===//
+//
+// 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 "dirfd.h"
+
+#include "src/__support/File/dir.h"
+#include "src/__support/common.h"
+
+#include <dirent.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, dirfd, (::DIR * dir)) {
+  auto *d = reinterpret_cast<__llvm_libc::Dir *>(dir);
+  return d->getfd();
+}
+
+} // namespace __llvm_libc
diff --git a/libc/src/dirent/dirfd.h b/libc/src/dirent/dirfd.h
@@ -0,0 +1,20 @@
+//===-- Implementation header of dirfd --------------------------*- 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_DIRENT_DIRFD_H
+#define LLVM_LIBC_SRC_DIRENT_DIRFD_H
+
+#include <dirent.h>
+
+namespace __llvm_libc {
+
+int dirfd(::DIR *dir);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_DIRENT_DIRFD_H
diff --git a/libc/src/dirent/opendir.cpp b/libc/src/dirent/opendir.cpp
@@ -0,0 +1,22 @@
+//===-- Implementation of opendir -----------------------------------------===//
+//
+// 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 "opendir.h"
+
+#include "src/__support/File/dir.h"
+#include "src/__support/common.h"
+
+#include <dirent.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(::DIR *, opendir, (const char *name)) {
+  return reinterpret_cast<::DIR *>(Dir::open(name));
+}
+
+} // namespace __llvm_libc
diff --git a/libc/src/dirent/opendir.h b/libc/src/dirent/opendir.h
@@ -0,0 +1,20 @@
+//===-- Implementation header of opendir ------------------------*- 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_DIRENT_OPENDIR_H
+#define LLVM_LIBC_SRC_DIRENT_OPENDIR_H
+
+#include <dirent.h>
+
+namespace __llvm_libc {
+
+::DIR *opendir(const char *name);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_DIRENT_OPENDIR_H
diff --git a/libc/src/dirent/readdir.cpp b/libc/src/dirent/readdir.cpp
@@ -0,0 +1,23 @@
+//===-- Implementation of readdir -----------------------------------------===//
+//
+// 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 "readdir.h"
+
+#include "src/__support/File/dir.h"
+#include "src/__support/common.h"
+
+#include <dirent.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(struct ::dirent *, readdir, (::DIR * dir)) {
+  auto *d = reinterpret_cast<__llvm_libc::Dir *>(dir);
+  return d->read();
+}
+
+} // namespace __llvm_libc
diff --git a/libc/src/dirent/readdir.h b/libc/src/dirent/readdir.h
@@ -0,0 +1,20 @@
+//===-- Implementation header of readdir ------------------------*- 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_DIRENT_READDIR_H
+#define LLVM_LIBC_SRC_DIRENT_READDIR_H
+
+#include <dirent.h>
+
+namespace __llvm_libc {
+
+struct ::dirent *readdir(DIR *dir);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_DIRENT_READDIR_H
diff --git a/libc/test/src/CMakeLists.txt b/libc/test/src/CMakeLists.txt
@@ -45,6 +45,7 @@ if(NOT LLVM_LIBC_FULL_BUILD)
   return()
 endif()
 
+add_subdirectory(dirent)
 # The signal API is currently disabled as signal.h is incorrect.
 # since assert uses the signal API, we disable assert also.
 # add_subdirectory(assert)

diff --git a/libc/test/src/dirent/CMakeLists.txt b/libc/test/src/dirent/CMakeLists.txt
@@ -0,0 +1,18 @@
+add_subdirectory(testdata)
+add_libc_testsuite(libc_dirent_unittests)
+
+add_libc_unittest(
+  dirent_test
+  SUITE
+    libc_dirent_unittests
+  SRCS
+    dirent_test.cpp
+  DEPENDS
+    libc.include.dirent
+    libc.src.__support.CPP.string_view
+    libc.src.dirent.closedir
+    libc.src.dirent.dirfd
+    libc.src.dirent.opendir
+    libc.src.dirent.readdir
+)
+
diff --git a/libc/test/src/dirent/dirent_test.cpp b/libc/test/src/dirent/dirent_test.cpp
@@ -0,0 +1,70 @@
+//===-- Unittests for functions from POSIX dirent.h -----------------------===//
+//
+// 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/__support/CPP/StringView.h"
+#include "src/dirent/closedir.h"
+#include "src/dirent/dirfd.h"
+#include "src/dirent/opendir.h"
+#include "src/dirent/readdir.h"
+
+#include "utils/UnitTest/Test.h"
+
+#include <dirent.h>
+#include <errno.h>
+
+using StringView = __llvm_libc::cpp::StringView;
+
+TEST(LlvmLibcDirentTest, SimpleOpenAndRead) {
+  ::DIR *dir = __llvm_libc::opendir("testdata");
+  ASSERT_TRUE(dir != nullptr);
+  // The file descriptors 0, 1 and 2 are reserved for standard streams.
+  // So, the file descriptor for the newly opened directory should be
+  // greater than 2.
+  ASSERT_GT(__llvm_libc::dirfd(dir), 2);
+
+  struct ::dirent *file1, *file2, *dir1, *dir2;
+  while (true) {
+    struct ::dirent *d = __llvm_libc::readdir(dir);
+    if (d == nullptr)
+      break;
+    if (StringView(d->d_name).equals("file1.txt"))
+      file1 = d;
+    if (StringView(d->d_name).equals("file2.txt"))
+      file2 = d;
+    if (StringView(d->d_name).equals("dir1"))
+      dir1 = d;
+    if (StringView(d->d_name).equals("dir2.txt"))
+      dir2 = d;
+  }
+
+  // Verify that we don't break out of the above loop in error.
+  ASSERT_EQ(errno, 0);
+
+  ASSERT_TRUE(file1 != nullptr);
+  ASSERT_TRUE(file2 != nullptr);
+  ASSERT_TRUE(dir1 != nullptr);
+  ASSERT_TRUE(dir2 != nullptr);
+
+  ASSERT_EQ(__llvm_libc::closedir(dir), 0);
+}
+
+TEST(LlvmLibcDirentTest, OpenNonExistentDir) {
+  errno = 0;
+  ::DIR *dir = __llvm_libc::opendir("___xyz123__.non_existent__");
+  ASSERT_TRUE(dir == nullptr);
+  ASSERT_EQ(errno, ENOENT);
+  errno = 0;
+}
+
+TEST(LlvmLibcDirentTest, OpenFile) {
+  errno = 0;
+  ::DIR *dir = __llvm_libc::opendir("testdata/file1.txt");
+  ASSERT_TRUE(dir == nullptr);
+  ASSERT_EQ(errno, ENOTDIR);
+  errno = 0;
+}
diff --git a/libc/test/src/dirent/testdata/CMakeLists.txt b/libc/test/src/dirent/testdata/CMakeLists.txt
@@ -0,0 +1,4 @@
+file(TOUCH ${CMAKE_CURRENT_BINARY_DIR}/file1.txt)
+file(TOUCH ${CMAKE_CURRENT_BINARY_DIR}/file2.txt)
+file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/dir1)
+file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/dir2)