diff --git a/lib/std/collections/ringbuffer.c3 b/lib/std/collections/ringbuffer.c3
index e60c79179..497e2991c 100644
--- a/lib/std/collections/ringbuffer.c3
+++ b/lib/std/collections/ringbuffer.c3
@@ -2,9 +2,9 @@ module collections::ringbuffer(<Type, SIZE>);
 
 struct RingBuffer
 {
-    Type[SIZE] buf;
-    usz written;
-    usz head;
+	Type[SIZE] buf;
+	usz written;
+	usz head;
 }
 
 fn void RingBuffer.init(&self) @inline
@@ -14,16 +14,16 @@ fn void RingBuffer.init(&self) @inline
 
 fn void RingBuffer.putc(&self, Type c)
 {
-    if (self.written < SIZE)
-    {
-	    self.buf[self.written] = c;
-    	self.written++;
-    }
-    else
-    {
-	    self.buf[self.head] = c;
-    	self.head = (self.head + 1) % SIZE;
-    }
+	if (self.written < SIZE)
+	{
+		self.buf[self.written] = c;
+		self.written++;
+	}
+	else
+	{
+		self.buf[self.head] = c;
+		self.head = (self.head + 1) % SIZE;
+	}
 }
 
 fn Type RingBuffer.getc(&self, usz index)
@@ -32,15 +32,15 @@ fn Type RingBuffer.getc(&self, usz index)
 	usz avail = SIZE - self.head;
 	if (index < avail)
 	{
-    	return self.buf[self.head + index];
+		return self.buf[self.head + index];
 	}
-    return self.buf[index - avail];
+	return self.buf[index - avail];
 }
 
 fn usz RingBuffer.get(&self, usz index, Type[] buffer)
 {
 	index %= SIZE;
-    if (self.written < SIZE)
+	if (self.written < SIZE)
 	{
 		if (index >= self.written) return 0;
 		usz end = self.written - index;
diff --git a/lib/std/libc/os/darwin.c3 b/lib/std/libc/os/darwin.c3
index 938c8014a..9c70a3ca7 100644
--- a/lib/std/libc/os/darwin.c3
+++ b/lib/std/libc/os/darwin.c3
@@ -31,3 +31,5 @@ struct Stat
 }
 
 extern fn int stat(ZString str, Stat* stat) @extern("stat64");
+
+extern fn CInt sysctl(CInt *name, CUInt namelen, void *oldp, usz *oldlenp, void *newp, usz newlen);
diff --git a/lib/std/libc/os/linux.c3 b/lib/std/libc/os/linux.c3
index 617e0cf59..8564233bc 100644
--- a/lib/std/libc/os/linux.c3
+++ b/lib/std/libc/os/linux.c3
@@ -57,3 +57,6 @@ struct Stat @if(!env::X86_64)
 }
 
 extern fn CInt stat(ZString path, Stat* stat);
+
+extern fn CInt get_nprocs();
+extern fn CInt get_nprocs_conf();
diff --git a/lib/std/libc/os/win32.c3 b/lib/std/libc/os/win32.c3
index a358efa59..643b60928 100644
--- a/lib/std/libc/os/win32.c3
+++ b/lib/std/libc/os/win32.c3
@@ -21,6 +21,28 @@ extern fn CFile _wfreopen(WString, WString, CFile);
 extern fn CInt _write(Fd fd, void* buffer, CUInt count);
 extern fn CInt _wremove(WString);
 
+struct SystemInfo
+{
+	union {
+		uint dwOemId;
+		struct {
+			ushort wProcessorArchitecture;
+			ushort wReserved;
+		}
+	}
+	uint     dwPageSize;
+	void*    lpMinimumApplicationAddress;
+	void*    lpMaximumApplicationAddress;
+	usz      dwActiveProcessorMask;
+	uint     dwNumberOfProcessors;
+	uint     dwProcessorType;
+	uint     dwAllocationGranularity;
+	ushort   wProcessorLevel;
+	ushort   wProcessorRevision;
+}
+
+extern fn CInt get_system_info(SystemInfo*) @extern("GetSystemInfo");
+
 // Aliases to simplify libc use
 macro Tm* localtime_r(Time_t* timer, Tm* buf) => _localtime64_s(buf, timer);
 macro CInt setjmp(JmpBuf* buffer) => _setjmp($$frameaddress(), buffer);
diff --git a/lib/std/threads/os/cpu.c3 b/lib/std/threads/os/cpu.c3
new file mode 100644
index 000000000..d803dc827
--- /dev/null
+++ b/lib/std/threads/os/cpu.c3
@@ -0,0 +1,69 @@
+// https://www.cprogramming.com/snippets/source-code/find-the-number-of-cpu-cores-for-windows-mac-or-linux
+
+module std::thread::cpu @if(env::DARWIN);
+import libc;
+
+const CTL_UNSPEC	= 0; /* unused */
+const CTL_KERN		= 1; /* "high kernel": proc, limits */
+const CTL_VM		= 2; /* virtual memory */
+const CTL_VFS		= 3; /* file system, mount type is next */
+const CTL_NET		= 4; /* network, see socket.h */
+const CTL_DEBUG		= 5; /* debugging parameters */
+const CTL_HW		= 6; /* generic cpu/io */
+const CTL_MACHDEP	= 7; /* machine dependent */
+const CTL_USER		= 8; /* user-level */
+const CTL_MAXID		= 9; /* number of valid top-level ids */
+
+const HW_MACHINE		= 1; /* string: machine class */
+const HW_MODEL			= 2; /* string: specific machine model */
+const HW_NCPU			= 3; /* int: number of cpus */
+const HW_BYTEORDER		= 4; /* int: machine byte order */
+const HW_PHYSMEM		= 5; /* int: total memory */
+const HW_USERMEM		= 6; /* int: non-kernel memory */
+const HW_PAGESIZE		= 7; /* int: software page size */
+const HW_DISKNAMES		= 8; /* strings: disk drive names */
+const HW_DISKSTATS		= 9; /* struct: diskstats[] */
+const HW_EPOCH			= 10; /* int: 0 for Legacy, else NewWorld */
+const HW_FLOATINGPT		= 11; /* int: has HW floating point? */
+const HW_MACHINE_ARCH	= 12; /* string: machine architecture */
+const HW_VECTORUNIT		= 13; /* int: has HW vector unit? */
+const HW_BUS_FREQ		= 14; /* int: Bus Frequency */
+const HW_CPU_FREQ		= 15; /* int: CPU Frequency */
+const HW_CACHELINE		= 16; /* int: Cache Line Size in Bytes */
+const HW_L1ICACHESIZE	= 17; /* int: L1 I Cache Size in Bytes */
+const HW_L1DCACHESIZE	= 18; /* int: L1 D Cache Size in Bytes */
+const HW_L2SETTINGS		= 19; /* int: L2 Cache Settings */
+const HW_L2CACHESIZE	= 20; /* int: L2 Cache Size in Bytes */
+const HW_L3SETTINGS		= 21; /* int: L3 Cache Settings */
+const HW_L3CACHESIZE	= 22; /* int: L3 Cache Size in Bytes */
+const HW_MAXID			= 23; /* number of valid hw ids */
+
+fn uint native_cpu()
+{
+	int[2] nm;
+	usz len = 4;
+	uint count;
+
+	nm = { CTL_HW, HW_NCPU };
+	libc::sysctl(&nm, 2, &count, &len, null, 0);
+	if (count < 1) count = 1;
+	return count;
+}
+
+module std::thread::cpu @if(env::LINUX);
+import libc;
+
+fn uint native_cpu()
+{
+	return libc::get_nprocs_conf();
+}
+
+module std::thread::cpu @if(env::WIN32);
+import libc;
+
+fn uint native_cpu()
+{
+	SystemInfo info;
+	libc::get_system_info(&info);
+	return info.dwNumberOfProcessors;
+}
\ No newline at end of file
diff --git a/lib/std/threads/os/thread_posix.c3 b/lib/std/threads/os/thread_posix.c3
index 02d64c8ab..d780aecae 100644
--- a/lib/std/threads/os/thread_posix.c3
+++ b/lib/std/threads/os/thread_posix.c3
@@ -150,7 +150,7 @@ fn void! NativeThread.create(&thread, ThreadFn thread_fn, void* arg)
 
 fn void! NativeThread.detach(thread)
 {
-	if (!posix::pthread_detach(thread)) return ThreadFault.DETACH_FAILED?;
+	if (posix::pthread_detach(thread)) return ThreadFault.DETACH_FAILED?;
 }
 
 fn void native_thread_exit(int result)
diff --git a/lib/std/threads/pool.c3 b/lib/std/threads/pool.c3
new file mode 100644
index 000000000..17b8b20cd
--- /dev/null
+++ b/lib/std/threads/pool.c3
@@ -0,0 +1,137 @@
+module std::thread::pool(<SIZE>);
+import std::thread;
+
+struct ThreadPool
+{
+	Mutex mu;
+	QueueItem[SIZE] queue;
+	usz qindex;
+	usz num_threads;
+	bitstruct : char {
+		bool initialized;
+		bool stop;
+		bool stop_now;
+	}
+
+	Thread[SIZE] pool;
+	ConditionVariable notify;
+}
+
+struct QueueItem
+{
+	ThreadFn func;
+	void* arg;
+}
+
+/**
+ * @require !self.initialized "ThreadPool must not be already initialized"
+ **/
+fn void! ThreadPool.init(&self)
+{
+	defer catch @ok(self.destroy());
+	*self = { .num_threads = SIZE, .initialized = true };
+	self.mu.init()!;
+	self.notify.init()!;
+	foreach (&thread : self.pool)
+	{
+		thread.create(&process_work, self)!;
+		// The thread resources will be cleaned up when the thread exits.
+		thread.detach()!;
+	}
+}
+
+/*
+ * Stop all the threads and cleanup the pool.
+ * Any pending work will be dropped.
+ */
+fn void! ThreadPool.destroy(&self)
+{
+	return self.@shutdown(stop_now);
+}
+
+/*
+ * Stop all the threads and cleanup the pool.
+ * Any pending work will be processed.
+ */
+fn void! ThreadPool.stop_and_destroy(&self)
+{
+	return self.@shutdown(stop);
+}
+
+macro void! ThreadPool.@shutdown(&self, #stop) @private
+{
+	if (self.initialized)
+	{
+		self.mu.lock()!;
+		self.#stop = true;
+		self.notify.broadcast()!;
+		self.mu.unlock()!;
+		// Wait for all threads to shutdown.
+		while (true)
+		{
+			self.mu.lock()!;
+			defer self.mu.unlock()!!;
+			if (self.num_threads == 0)
+			{
+				break;
+			}
+			self.notify.signal()!;
+		}
+		self.mu.destroy()!;
+		self.initialized = false;
+	}
+}
+
+/*
+ * Push a new job to the pool.
+ * Returns whether the queue is full, in which case the job is ignored.
+ */
+fn void! ThreadPool.push(&self, ThreadFn func, void* arg)
+{
+	while (true)
+	{
+		self.mu.lock()!;
+		defer self.mu.unlock()!!;
+		if (self.qindex < SIZE)
+		{
+			self.queue[self.qindex] = { .func = func, .arg = arg };
+			self.qindex++;
+			// Notify the threads that work is available.
+			self.notify.broadcast()!;
+			return;
+		}
+	}
+}
+
+fn int process_work(void* arg) @private
+{
+	ThreadPool* self = arg;
+	while (true)
+	{
+		self.mu.lock()!!;
+		// Wait for work.
+		while (self.qindex == 0)
+		{
+			if (self.stop)
+			{
+				// Shutdown requested.
+				self.num_threads--;
+				self.mu.unlock()!!;
+				return 0;
+			}
+			self.notify.wait(&self.mu)!!;
+			if (self.stop_now)
+			{
+				// Shutdown requested.
+				self.num_threads--;
+				self.mu.unlock()!!;
+				return 0;
+			}
+		}
+		// Process the job.
+		self.qindex--;
+		QueueItem item = self.queue[self.qindex];
+		self.mu.unlock()!!;
+		item.func(item.arg);
+	}
+}
\ No newline at end of file
diff --git a/lib/std/threads/thread.c3 b/lib/std/threads/thread.c3
index f1d6c194b..402658b58 100644
--- a/lib/std/threads/thread.c3
+++ b/lib/std/threads/thread.c3
@@ -1,4 +1,5 @@
 module std::thread;
+import std::thread::cpu;
 import std::thread::os;
 
 def MutexType = distinct int;
@@ -65,3 +66,4 @@ macro void! sleep(double s) @maydiscard => os::native_sleep(s);
 macro void! sleep_ms(ulong ms) @maydiscard  => os::native_sleep_ms(ms);
 macro void! sleep_ns(ulong ns) @maydiscard  => os::native_sleep_nano(ns);
 
+macro uint num_cpu() => cpu::native_cpu();
\ No newline at end of file
diff --git a/test/unit/stdlib/collections/ringbuffer.c3 b/test/unit/stdlib/collections/ringbuffer.c3
index c14ba71ee..88ee3cec1 100644
--- a/test/unit/stdlib/collections/ringbuffer.c3
+++ b/test/unit/stdlib/collections/ringbuffer.c3
@@ -6,21 +6,21 @@ def Buffer = RingBuffer(<char, 4>);
 
 fn void putc_getc()
 {
-    Buffer rb;
-    rb.init();
-    rb.putc(1);
-    rb.putc(2);
-    rb.putc(3);
-    rb.putc(4);
+	Buffer rb;
+	rb.init();
+	rb.putc(1);
+	rb.putc(2);
+	rb.putc(3);
+	rb.putc(4);
 
-    assert(rb.getc(0) == 1);
-    assert(rb.getc(1) == 2);
-    assert(rb.getc(2) == 3);
-    assert(rb.getc(3) == 4);
+	assert(rb.getc(0) == 1);
+	assert(rb.getc(1) == 2);
+	assert(rb.getc(2) == 3);
+	assert(rb.getc(3) == 4);
 
-    rb.putc(5);
-    assert(rb.getc(0) == 2);
-    assert(rb.getc(1) == 3);
+	rb.putc(5);
+	assert(rb.getc(0) == 2);
+	assert(rb.getc(1) == 3);
 	assert(rb.getc(2) == 4);
 	assert(rb.getc(3) == 5);
 }
\ No newline at end of file
diff --git a/test/unit/stdlib/threads/pool.c3 b/test/unit/stdlib/threads/pool.c3
new file mode 100644
index 000000000..ab72d7bf3
--- /dev/null
+++ b/test/unit/stdlib/threads/pool.c3
@@ -0,0 +1,67 @@
+module thread_pool_test;
+import std::io;
+import std::thread;
+import std::thread::pool;
+
+def Pool = ThreadPool(<4>);
+
+fn void! init_destroy() @test
+{
+	for (usz i = 0; i < 20; i++)
+	{
+		Pool pool;
+		pool.init()!;
+		pool.destroy()!;
+	}
+}
+
+fn void! push_destroy() @test
+{
+	for (usz i = 0; i < 20; i++)
+	{
+		x = 0;
+		int y = 20;
+		Pool pool;
+		pool.init()!;
+		defer pool.destroy()!!;
+		work_done.lock()!!;
+		pool.push(&do_work, &y)!;
+		work_done.lock()!!;
+		assert(x == y, "%d: %d != %d", i, x, y);
+		work_done.unlock()!!;
+	}
+}
+
+fn void! push_stop() @test
+{
+	for (usz i = 0; i < 20; i++)
+	{
+		x = 0;
+		int y = 20;
+		Pool pool;
+		pool.init()!;
+		work_done.lock()!!;
+		pool.push(&do_work, &y)!;
+		pool.stop_and_destroy()!!;
+		assert(x == y, "%d: %d != %d", i, x, y);
+	}
+}
+
+int x;
+
+Mutex work_done;
+
+static initialize {
+	work_done.init()!!;
+}
+
+static finalize {
+	work_done.destroy()!!;
+}
+
+fn int do_work(void* arg)
+{
+	x = *(int*)arg;
+	work_done.unlock()!!;
+	return 0;
+}
\ No newline at end of file
diff --git a/test/unit/stdlib/threads/simple_thread.c3 b/test/unit/stdlib/threads/simple_thread.c3
index 2d541420b..721397048 100644
--- a/test/unit/stdlib/threads/simple_thread.c3
+++ b/test/unit/stdlib/threads/simple_thread.c3
@@ -63,10 +63,7 @@ fn void! testrun_mutex_timeout() @test
 	Mutex m;
 	m.init()!;
 	m.lock()!;
-	if (catch m.lock_timeout(100))
-	{
-	}
-	else
+	if (try m.lock_timeout(100))
 	{
 		assert(false, "lock_timeout should fail");
 	}