diff --git a/.circleci/config.yml b/.circleci/config.yml
index f5e89a89..4f0a9e99 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -2,10 +2,11 @@ version: 2
 
 jobs:
   omnibus_osx_llvm:
+    resource_class: macos.x86.medium.gen2
     macos:
-      xcode: 12.4.0
+      xcode: 13.4.1
     environment:
-      LLVM_VERSION: 10.0.0
+      LLVM_VERSION: 15.0.7
       MACOSX_DEPLOYMENT_TARGET: 10.11
     shell: /bin/bash --login -eo pipefail
     steps:
diff --git a/omnibus/config/software/llvm.rb b/omnibus/config/software/llvm.rb
index 5fd2634f..9a9fda05 100644
--- a/omnibus/config/software/llvm.rb
+++ b/omnibus/config/software/llvm.rb
@@ -1,5 +1,5 @@
 name "llvm"
-LLVM_VERSION = (ENV['LLVM_VERSION'] || "10.0.0").strip
+LLVM_VERSION = (ENV['LLVM_VERSION'] || "15.0.7").strip
 default_version LLVM_VERSION
 skip_transitive_dependency_licensing true
 
@@ -18,7 +18,17 @@
          md5: "693cefdc49d618f828144486a18b473f"
 end
 
-relative_path "llvm-#{version}.src"
+version "15.0.7" do
+  source url: "https://github.com/llvm/llvm-project/releases/download/llvmorg-#{version}/llvm-project-#{version}.src.tar.xz",
+         md5: "bac436dbd5d37e38d3da75b03629053c"
+end
+
+if version == "15.0.7"
+  # This is bringing the whole project because flags weren't sufficient to prevent certain parts from being fetched by the build system.
+  relative_path "llvm-project-#{version}.src/llvm"
+else
+  relative_path "llvm-#{version}.src"
+end
 
 whitelist_file "lib/BugpointPasses.dylib"
 whitelist_file "lib/libLTO.dylib"
@@ -27,7 +37,7 @@
 
 env = with_standard_compiler_flags(with_embedded_path)
 
-llvm_build_dir = "#{build_dir}/build-llvm"
+llvm_build_dir = "#{project_dir}/build-llvm"
 
 build do
   mkdir llvm_build_dir
@@ -47,9 +57,12 @@
     " -DLLVM_INCLUDE_TESTS=OFF" \
     " -DLLVM_ENABLE_Z3_SOLVER=OFF" \
     " -DLLVM_ENABLE_LIBXML2=OFF" \
+    " -DLLVM_BUILD_BENCHMARKS=OFF" \
+    " -DLLVM_INCLUDE_BENCHMARKS=OFF" \
+    " -DLLVM_ENABLE_ZSTD=OFF" \
     "#{' -DPYTHON_EXECUTABLE=$(which python2.7)' if centos? }"\
     " #{project_dir}", env: env, cwd: llvm_build_dir
-  command "cmake --build .", env: env, cwd: llvm_build_dir
+  command "cmake --build . --parallel $(sysctl -n hw.logicalcpu)", env: env, cwd: llvm_build_dir
   command "cmake -DCMAKE_INSTALL_PREFIX=#{install_dir} -P cmake_install.cmake", env: env, cwd: llvm_build_dir
   command "cmake --build . --target install", env: env, cwd: llvm_build_dir
 end