diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 593e99611..014e277f8 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -7,7 +7,7 @@ on:
     branches: [ master, dev ]
 
 env:
-  LLVM_RELEASE_VERSION_WINDOWS: 18
+  LLVM_RELEASE_VERSION_WINDOWS: 21
   LLVM_RELEASE_VERSION_MAC: 18
   LLVM_RELEASE_VERSION_LINUX: 19
   LLVM_RELEASE_VERSION_OPENBSD: 19
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 922676abe..d26747fd7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -142,11 +142,11 @@ if(C3_WITH_LLVM)
         endif()
         FetchContent_Declare(
                 LLVM_Windows
-                URL https://github.com/c3lang/win-llvm/releases/download/llvm_19_1_5/llvm-19.1.5-windows-amd64-msvc17-libcmt.7z
+                URL https://github.com/c3lang/win-llvm/releases/download/llvm_21_1_8/llvm-21.1.8-windows-amd64-msvc17-libcmt.7z
         )
         FetchContent_Declare(
                 LLVM_Windows_debug
-                URL https://github.com/c3lang/win-llvm/releases/download/llvm_19_1_5/llvm-19.1.5-windows-amd64-msvc17-libcmt-dbg.7z
+                URL https://github.com/c3lang/win-llvm/releases/download/llvm_21_1_8/llvm-21.1.8-windows-amd64-msvc17-libcmt-dbg.7z
         )
         if(CMAKE_BUILD_TYPE STREQUAL "Debug")
             message("Loading Windows LLVM debug libraries, this may take a while...")