diff --git a/.github/workflows/win.yml b/.github/workflows/win.yml
index 9fce9f93aa44..3ef4cccb8739 100644
--- a/.github/workflows/win.yml
+++ b/.github/workflows/win.yml
@@ -7,7 +7,7 @@ concurrency:
   cancel-in-progress: ${{ github.ref != 'refs/heads/master' }}
 
 env:
-  CI_LLVM_VERSION: "17.0.2"
+  CI_LLVM_VERSION: "18.1.0-rc1"
 
 jobs:
   x86_64-windows-libs:
@@ -177,30 +177,13 @@ jobs:
           path: llvm
           key: llvm-libs-${{ env.CI_LLVM_VERSION }}-msvc
 
-      - name: Download LLVM
-        if: steps.cache-llvm-libs.outputs.cache-hit != 'true'
-        run: |
-          iwr https://github.com/llvm/llvm-project/releases/download/llvmorg-${{ env.CI_LLVM_VERSION }}/llvm-${{ env.CI_LLVM_VERSION }}.src.tar.xz -OutFile llvm.tar.xz
-          (Get-FileHash -Algorithm SHA256 .\llvm.tar.xz).hash -eq "D820E63BC3A6F4F833EC69A1EF49A2E81992E90BC23989F98946914B061AB6C7"
-          7z x llvm.tar.xz
-          7z x llvm.tar
-          mv llvm-* llvm-src
-
-      - name: Download LLVM's CMake files
-        if: steps.cache-llvm-libs.outputs.cache-hit != 'true'
-        run: |
-          iwr https://github.com/llvm/llvm-project/releases/download/llvmorg-${{ env.CI_LLVM_VERSION }}/cmake-${{ env.CI_LLVM_VERSION }}.src.tar.xz -OutFile cmake.tar.xz
-          (Get-FileHash -Algorithm SHA256 .\cmake.tar.xz).hash -eq "B6D83C91F12757030D8361DEDC5DD84357B3EDB8DA406B5D0850DF8B6F7798B1"
-          7z x cmake.tar.xz
-          7z x cmake.tar
-          mv cmake-* cmake
-
       - name: Build LLVM
         if: steps.cache-llvm-libs.outputs.cache-hit != 'true'
         run: |
+          git clone --config core.autocrlf=false -b llvmorg-${{ env.CI_LLVM_VERSION }} --depth 1 https://github.com/llvm/llvm-project.git
           mkdir llvm-build
           cd llvm-build
-          cmake ..\llvm-src -Thost=x64 -DLLVM_TARGETS_TO_BUILD="X86;AArch64" -DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreaded -DBUILD_SHARED_LIBS=OFF -DCMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH=OFF -DLLVM_INCLUDE_BENCHMARKS=OFF -DLLVM_INCLUDE_TESTS=OFF -DLLVM_ENABLE_ZSTD=OFF
+          cmake ..\llvm-project\llvm -Thost=x64 -DLLVM_TARGETS_TO_BUILD="X86;AArch64" -DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreaded -DBUILD_SHARED_LIBS=OFF -DCMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH=OFF -DLLVM_INCLUDE_BENCHMARKS=OFF -DLLVM_INCLUDE_TESTS=OFF -DLLVM_ENABLE_ZSTD=OFF
           cmake --build . --config Release
           cmake "-DCMAKE_INSTALL_PREFIX=$(pwd)\..\llvm" -P cmake_install.cmake
 
@@ -235,7 +218,7 @@ jobs:
     uses: ./.github/workflows/win_build_portable.yml
     with:
       release: false
-      llvm_version: "17.0.2"
+      llvm_version: "18.1.0-rc1"
 
   x86_64-windows-test:
     runs-on: windows-2022
@@ -288,7 +271,7 @@ jobs:
     uses: ./.github/workflows/win_build_portable.yml
     with:
       release: true
-      llvm_version: "17.0.2"
+      llvm_version: "18.1.0-rc1"
 
   x86_64-windows-installer:
     if: github.repository_owner == 'crystal-lang' && (startsWith(github.ref, 'refs/tags/') || startsWith(github.ref, 'refs/heads/ci/'))
diff --git a/etc/win-ci/build-llvm.ps1 b/etc/win-ci/build-llvm.ps1
index b544e9eba784..9335cfe9abe4 100644
--- a/etc/win-ci/build-llvm.ps1
+++ b/etc/win-ci/build-llvm.ps1
@@ -16,7 +16,7 @@ if (-not $Dynamic) {
 Setup-Git -Path $BuildTree -Url https://github.com/llvm/llvm-project.git -Ref llvmorg-$Version
 
 Run-InDirectory $BuildTree\build {
-    $args = "-Thost=x64 -DLLVM_TARGETS_TO_BUILD=""$($TargetsToBuild -join ';')"" -DCMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH=OFF -DLLVM_INCLUDE_BENCHMARKS=OFF -DLLVM_INCLUDE_DOCS=OFF -DLLVM_INCLUDE_TESTS=OFF -DLLVM_ENABLE_ZSTD=OFF"
+    $args = "-Thost=x64 -DLLVM_TARGETS_TO_BUILD=$($TargetsToBuild -join ';') -DCMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH=OFF -DLLVM_INCLUDE_BENCHMARKS=OFF -DLLVM_INCLUDE_DOCS=OFF -DLLVM_INCLUDE_TESTS=OFF -DLLVM_ENABLE_ZSTD=OFF"
     if ($Dynamic) {
         $args = "-DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreadedDLL $args"
     } else {
diff --git a/src/llvm/ext/llvm-versions.txt b/src/llvm/ext/llvm-versions.txt
index 7c8773c02212..92ae5ecbaa5a 100644
--- a/src/llvm/ext/llvm-versions.txt
+++ b/src/llvm/ext/llvm-versions.txt
@@ -1 +1 @@
-17.0 16.0 15.0 14.0 13.0 12.0 11.1 11.0 10.0 9.0 8.0
+18.1 17.0 16.0 15.0 14.0 13.0 12.0 11.1 11.0 10.0 9.0 8.0
diff --git a/src/llvm/lib_llvm.cr b/src/llvm/lib_llvm.cr
index d5e7c2488002..b68e212d2052 100644
--- a/src/llvm/lib_llvm.cr
+++ b/src/llvm/lib_llvm.cr
@@ -35,7 +35,7 @@
 
   @[Link(ldflags: {{ llvm_ldflags }})]
   lib LibLLVM
-    VERSION = {{ llvm_version.strip.gsub(/git/, "") }}
+    VERSION = {{ llvm_version.strip.gsub(/git/, "").gsub(/rc.*/, "") }}
     BUILT_TARGETS = {{ llvm_targets.strip.downcase.split(' ').map(&.id.symbolize) }}
   end
 {% end %}