diff --git a/libc/src/threads/thrd_create.h b/libc/src/threads/thrd_create.h
@@ -0,0 +1,20 @@
+//===------- Implementation header for thrd_create function ------ *-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_THREADS_LINUX_THRD_CREATE_H
+#define LLVM_LIBC_SRC_THREADS_LINUX_THRD_CREATE_H
+
+#include "include/threads.h"
+
+namespace __llvm_libc {
+
+int thrd_create(thrd_t *thread, thrd_start_t func, void *arg);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_THREADS_LINUX_THRD_CREATE_H
diff --git a/libc/src/threads/thrd_join.h b/libc/src/threads/thrd_join.h
@@ -0,0 +1,20 @@
+//===-------- Implementation header for thrd_join function ------- *-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_THREADS_LINUX_THRD_JOIN_H
+#define LLVM_LIBC_SRC_THREADS_LINUX_THRD_JOIN_H
+
+#include "include/threads.h"
+
+namespace __llvm_libc {
+
+int thrd_join(thrd_t *thread, int *retval);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_THREADS_LINUX_THRD_JOIN_H
diff --git a/libc/test/src/CMakeLists.txt b/libc/test/src/CMakeLists.txt
@@ -3,3 +3,4 @@ add_subdirectory(signal)
 add_subdirectory(stdlib)
 add_subdirectory(string)
 add_subdirectory(sys)
+add_subdirectory(threads)
diff --git a/libc/test/src/threads/CMakeLists.txt b/libc/test/src/threads/CMakeLists.txt
@@ -0,0 +1,16 @@
+add_libc_testsuite(libc_threads_unittests)
+
+add_libc_unittest(
+  thrd_test
+  SUITE
+    libc_threads_unittests
+  SRCS
+    thrd_test.cpp
+  DEPENDS
+    __errno_location
+    mmap
+    munmap
+    threads_h
+    thrd_create
+    thrd_join
+)
diff --git a/libc/test/src/threads/thrd_test.cpp b/libc/test/src/threads/thrd_test.cpp
@@ -0,0 +1,52 @@
+//===---------------------- Unittests for thrd_t --------------------------===//
+//
+// 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/threads.h"
+#include "src/threads/thrd_create.h"
+#include "src/threads/thrd_join.h"
+#include "utils/UnitTest/Test.h"
+
+static constexpr int thread_count = 1000;
+static int counter = 0;
+static int thread_func(void *) {
+  ++counter;
+  return 0;
+}
+
+TEST(ThreadTest, CreateAndJoin) {
+  for (counter = 0; counter <= thread_count;) {
+    thrd_t thread;
+    int old_counter_val = counter;
+    ASSERT_EQ(__llvm_libc::thrd_create(&thread, thread_func, nullptr),
+              (int)thrd_success);
+    int retval = thread_count + 1; // Start with a retval we dont expect.
+    ASSERT_EQ(__llvm_libc::thrd_join(&thread, &retval), (int)thrd_success);
+    ASSERT_EQ(retval, 0);
+    ASSERT_EQ(counter, old_counter_val + 1);
+  }
+}
+
+static int return_arg(void *arg) { return *reinterpret_cast<int *>(arg); }
+
+TEST(ThreadTest, SpawnAndJoin) {
+  thrd_t thread_list[thread_count];
+  int args[thread_count];
+
+  for (int i = 0; i < thread_count; ++i) {
+    args[i] = i;
+    ASSERT_EQ(__llvm_libc::thrd_create(thread_list + i, return_arg, args + i),
+              (int)thrd_success);
+  }
+
+  for (int i = 0; i < thread_count; ++i) {
+    int retval = thread_count + 1; // Start with a retval we dont expect.
+    ASSERT_EQ(__llvm_libc::thrd_join(&thread_list[i], &retval),
+              (int)thrd_success);
+    ASSERT_EQ(retval, i);
+  }
+}