diff --git a/mlir/include/mlir/ExecutionEngine/AsyncRuntime.h b/mlir/include/mlir/ExecutionEngine/AsyncRuntime.h
--- a/mlir/include/mlir/ExecutionEngine/AsyncRuntime.h
+++ b/mlir/include/mlir/ExecutionEngine/AsyncRuntime.h
@@ -32,6 +32,9 @@
 #define MLIR_ASYNCRUNTIME_DEFINE_FUNCTIONS
 #endif // _WIN32
 
+namespace mlir {
+namespace runtime {
+
 //===----------------------------------------------------------------------===//
 // Async runtime API.
 //===----------------------------------------------------------------------===//
@@ -102,4 +105,7 @@
 
 extern "C" MLIR_ASYNCRUNTIME_EXPORT void mlirAsyncRuntimePrintCurrentThreadId();
 
+} // namespace runtime
+} // namespace mlir
+
 #endif // MLIR_EXECUTIONENGINE_ASYNCRUNTIME_H_
diff --git a/mlir/lib/ExecutionEngine/AsyncRuntime.cpp b/mlir/lib/ExecutionEngine/AsyncRuntime.cpp
--- a/mlir/lib/ExecutionEngine/AsyncRuntime.cpp
+++ b/mlir/lib/ExecutionEngine/AsyncRuntime.cpp
@@ -24,10 +24,14 @@
 #include <thread>
 #include <vector>
 
+using namespace mlir::runtime;
+
 //===----------------------------------------------------------------------===//
 // Async runtime API.
 //===----------------------------------------------------------------------===//
 
+namespace mlir {
+namespace runtime {
 namespace {
 
 // Forward declare class defined below.
@@ -66,12 +70,6 @@
   std::atomic<int32_t> numRefCountedObjects;
 };
 
-// Returns the default per-process instance of an async runtime.
-AsyncRuntime *getDefaultAsyncRuntimeInstance() {
-  static auto runtime = std::make_unique<AsyncRuntime>();
-  return runtime.get();
-}
-
 // -------------------------------------------------------------------------- //
 // A base class for all reference counted objects created by the async runtime.
 // -------------------------------------------------------------------------- //
@@ -110,6 +108,12 @@
 
 } // namespace
 
+// Returns the default per-process instance of an async runtime.
+static AsyncRuntime *getDefaultAsyncRuntimeInstance() {
+  static auto runtime = std::make_unique<AsyncRuntime>();
+  return runtime.get();
+}
+
 struct AsyncToken : public RefCounted {
   // AsyncToken created with a reference count of 2 because it will be returned
   // to the `async.execute` caller and also will be later on emplaced by the
@@ -140,6 +144,9 @@
   std::vector<std::function<void()>> awaiters;
 };
 
+} // namespace runtime
+} // namespace mlir
+
 // Adds references to reference counted runtime object.
 extern "C" void mlirAsyncRuntimeAddRef(RefCountedObjPtr ptr, int32_t count) {
   RefCounted *refCounted = static_cast<RefCounted *>(ptr);