diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cd8694409..4d615b791 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -398,8 +398,10 @@ jobs:
             python_ver: "3.10"
             simd: avx2,f16c
             batched: b8_AVX2,b8_AVX512,b16_AVX512
-            setenvs: export LLVM_VERSION=17.0.6
-                            LLVM_DISTRO_NAME=ubuntu-22.04
+            setenvs: export LLVM_VERSION=18.1.8
+                            xLLVM_VERSION=17.0.6
+                            LLVM_DISTRO_NAME=ubuntu-18.04
+                            xLLVM_DISTRO_NAME=ubuntu-22.04
                             OPENCOLORIO_VERSION=main
                             PUGIXML_VERSION=master
           - desc: clang14/C++17 llvm14 py3.8 avx2 batch-b16avx512
diff --git a/INSTALL.md b/INSTALL.md
index d95b0db2e..17d608ef2 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -47,8 +47,8 @@ NEW or CHANGED dependencies since the last major release are **bold**.
     $OpenImageIO_ROOT/lib to be in your LD_LIBRARY_PATH (or
     DYLD_LIBRARY_PATH on OS X).
 
-* [LLVM](http://www.llvm.org) 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, including
-  clang libraries.
+* [LLVM](http://www.llvm.org) 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19,
+  including clang libraries.
 
 * (optional) For GPU rendering on NVIDIA GPUs:
     * [OptiX](https://developer.nvidia.com/rtx/ray-tracing/optix) 7.0 or higher.
diff --git a/src/cmake/externalpackages.cmake b/src/cmake/externalpackages.cmake
index a652739cb..36aa570bf 100644
--- a/src/cmake/externalpackages.cmake
+++ b/src/cmake/externalpackages.cmake
@@ -58,7 +58,7 @@ checked_find_package (pugixml REQUIRED
 # LLVM library setup
 checked_find_package (LLVM REQUIRED
                       VERSION_MIN 9.0
-                      VERSION_MAX 18.9
+                      VERSION_MAX 19.9
                       PRINT LLVM_SYSTEM_LIBRARIES CLANG_LIBRARIES)
 # ensure include directory is added (in case of non-standard locations
 include_directories (BEFORE SYSTEM "${LLVM_INCLUDES}")
diff --git a/src/liboslexec/llvm_passes.h b/src/liboslexec/llvm_passes.h
index 43c7a7289..d0a1b7502 100644
--- a/src/liboslexec/llvm_passes.h
+++ b/src/liboslexec/llvm_passes.h
@@ -12,6 +12,7 @@
 #include <llvm/IR/IRBuilder.h>
 #include <llvm/IR/Instruction.h>
 #include <llvm/IR/Instructions.h>
+#include <llvm/IR/Module.h>
 #include <llvm/IR/PassManager.h>
 #include <llvm/IR/Type.h>
 #include <llvm/Pass.h>
diff --git a/src/liboslexec/llvm_util.cpp b/src/liboslexec/llvm_util.cpp
index de41e217f..1317de048 100644
--- a/src/liboslexec/llvm_util.cpp
+++ b/src/liboslexec/llvm_util.cpp
@@ -1173,7 +1173,12 @@ static llvm::StringMap<bool> sCpuFeatures;
 static bool
 populateCpuFeatures()
 {
+#if OSL_LLVM_VERSION >= 190
+    sCpuFeatures = llvm::sys::getHostCPUFeatures();
+    return true;
+#else
     return llvm::sys::getHostCPUFeatures(sCpuFeatures);
+#endif
 }
 
 
@@ -1551,10 +1556,12 @@ LLVM_Util::make_jit_execengine(std::string* err, TargetISA requestedISA,
 #if OSL_LLVM_VERSION < 120
     options.StackAlignmentOverride = 0;
 #endif
-    options.FunctionSections    = true;
-    options.UseInitArray        = false;
-    options.FloatABIType        = llvm::FloatABI::Default;
+    options.FunctionSections = true;
+    options.UseInitArray     = false;
+    options.FloatABIType     = llvm::FloatABI::Default;
+#if OSL_LLVM_VERSION < 190
     options.RelaxELFRelocations = false;
+#endif
     //options.DebuggerTuning = llvm::DebuggerKind::GDB;
 
     // TODO: Find equivalent function for PrintMachineCode post LLVM 12