diff --git a/LEGO1/omni/include/mxthread.h b/LEGO1/omni/include/mxthread.h
index 5f04a26c..64d47884 100644
--- a/LEGO1/omni/include/mxthread.h
+++ b/LEGO1/omni/include/mxthread.h
@@ -5,6 +5,8 @@
 #include "mxsemaphore.h"
 #include "mxtypes.h"
 
+#include <SDL3/SDL_thread.h>
+
 class MxCore;
 
 // VTABLE: LEGO1 0x100dc860
@@ -33,10 +35,9 @@ public:
 private:
 	static unsigned ThreadProc(void* p_thread);
 
-	MxULong m_hThread;       // 0x04
-	MxU32 m_threadId;        // 0x08
-	MxBool m_running;        // 0x0c
-	MxSemaphore m_semaphore; // 0x10
+	SDL_Thread* m_thread;
+	MxBool m_running;
+	MxSemaphore m_semaphore;
 
 protected:
 	MxCore* m_target; // 0x18
diff --git a/LEGO1/omni/src/system/mxsemaphore.cpp b/LEGO1/omni/src/system/mxsemaphore.cpp
index 96398150..edeb0f60 100644
--- a/LEGO1/omni/src/system/mxsemaphore.cpp
+++ b/LEGO1/omni/src/system/mxsemaphore.cpp
@@ -16,9 +16,11 @@ MxResult MxSemaphore::Init(MxU32 p_initialCount, MxU32 p_maxCount)
 {
 	// [library:synchronization] No support for max count, but shouldn't be necessary
 	MxResult result = FAILURE;
+
 	if ((m_semaphore = SDL_CreateSemaphore(p_initialCount))) {
 		result = SUCCESS;
 	}
+
 	return result;
 }
 
diff --git a/LEGO1/omni/src/system/mxthread.cpp b/LEGO1/omni/src/system/mxthread.cpp
index 455ce8f3..c84cace6 100644
--- a/LEGO1/omni/src/system/mxthread.cpp
+++ b/LEGO1/omni/src/system/mxthread.cpp
@@ -2,39 +2,45 @@
 
 #include "decomp.h"
 
-#include <process.h>
-#include <windows.h>
+#include <SDL3/SDL_timer.h>
 
 DECOMP_SIZE_ASSERT(MxThread, 0x1c)
 
 // FUNCTION: LEGO1 0x100bf510
 MxThread::MxThread()
 {
-	m_hThread = NULL;
+	m_thread = NULL;
 	m_running = TRUE;
-	m_threadId = 0;
 }
 
 // FUNCTION: LEGO1 0x100bf5a0
 MxThread::~MxThread()
 {
-	if (m_hThread) {
-		CloseHandle((HANDLE) m_hThread);
+	if (m_thread) {
+		SDL_WaitThread(m_thread, NULL);
 	}
 }
 
-typedef unsigned(__stdcall* ThreadFunc)(void*);
-
 // FUNCTION: LEGO1 0x100bf610
 MxResult MxThread::Start(MxS32 p_stack, MxS32 p_flag)
 {
 	MxResult result = FAILURE;
 
 	if (m_semaphore.Init(0, 1) == SUCCESS) {
-		if ((m_hThread =
-				 _beginthreadex(NULL, p_stack << 2, (ThreadFunc) &MxThread::ThreadProc, this, p_flag, &m_threadId))) {
+		const SDL_PropertiesID props = SDL_CreateProperties();
+		SDL_SetProperty(
+			props,
+			SDL_PROP_THREAD_CREATE_ENTRY_FUNCTION_POINTER,
+			(SDL_FunctionPointer) &MxThread::ThreadProc
+		);
+		SDL_SetProperty(props, SDL_PROP_THREAD_CREATE_USERDATA_POINTER, this);
+		SDL_SetNumberProperty(props, SDL_PROP_THREAD_CREATE_STACKSIZE_NUMBER, p_stack << 2);
+
+		if ((m_thread = SDL_CreateThreadWithProperties(props))) {
 			result = SUCCESS;
 		}
+
+		SDL_DestroyProperties(props);
 	}
 
 	return result;
@@ -43,7 +49,7 @@ MxResult MxThread::Start(MxS32 p_stack, MxS32 p_flag)
 // FUNCTION: LEGO1 0x100bf660
 void MxThread::Sleep(MxS32 p_milliseconds)
 {
-	::Sleep(p_milliseconds);
+	SDL_Delay(p_milliseconds);
 }
 
 // FUNCTION: LEGO1 0x100bf670
diff --git a/README.md b/README.md
index 694f7ac4..b2dd8c38 100644
--- a/README.md
+++ b/README.md
@@ -24,7 +24,7 @@ To achieve our goal of platform independence, we need to replace any Windows-onl
 | - | - | - | - |
 | [Smacker](https://github.com/isledecomp/isle/tree/master/3rdparty/smacker) | [libsmacker](https://github.com/foxtacles/libsmacker) | ✅ | [Remarks](https://github.com/search?q=repo%3Aisledecomp%2Fisle-portable%20%22%2F%2F%20%5Blibrary%3Alibsmacker%5D%22&type=code) |
 | Filesystem | C standard library | ❌ | [Remarks](https://github.com/search?q=repo%3Aisledecomp%2Fisle-portable+%22%2F%2F+%5Blibrary%3Afilesystem%5D%22&type=code) |
-| Threads, Mutexes (Synchronization) | [SDL3](https://www.libsdl.org/) | ❌ | [Remarks](https://github.com/search?q=repo%3Aisledecomp%2Fisle-portable+%22%2F%2F+%5Blibrary%3Asynchronization%5D%22&type=code) |
+| Threads, Mutexes (Synchronization) | [SDL3](https://www.libsdl.org/) | ✅ | [Remarks](https://github.com/search?q=repo%3Aisledecomp%2Fisle-portable+%22%2F%2F+%5Blibrary%3Asynchronization%5D%22&type=code) |
 | Keyboard, Mouse, Joystick, DirectInput (Input) | [SDL3](https://www.libsdl.org/) | ❌ | [Remarks](https://github.com/search?q=repo%3Aisledecomp%2Fisle-portable+%22%2F%2F+%5Blibrary%3Ainput%5D%22&type=code) |
 | WinMM, DirectSound (Audio) | [SDL3](https://www.libsdl.org/) | ❌ | [Remarks](https://github.com/search?q=repo%3Aisledecomp%2Fisle-portable+%22%2F%2F+%5Blibrary%3Aaudio%5D%22&type=code) |
 | DirectDraw (2D video) | [SDL3](https://www.libsdl.org/) | ❌ | [Remarks](https://github.com/search?q=repo%3Aisledecomp%2Fisle-portable+%22%2F%2F+%5Blibrary%3A2d%5D%22&type=code) |