diff --git a/mlir/lib/IR/MLIRContext.cpp b/mlir/lib/IR/MLIRContext.cpp
--- a/mlir/lib/IR/MLIRContext.cpp
+++ b/mlir/lib/IR/MLIRContext.cpp
@@ -262,7 +262,7 @@
   //===--------------------------------------------------------------------===//
 
   /// The thread pool to use when processing MLIR tasks in parallel.
-  llvm::ThreadPool threadPool;
+  llvm::Optional<llvm::ThreadPool> threadPool;
 
   /// This is a list of dialects that are created referring to this context.
   /// The MLIRContext owns the objects.
@@ -334,7 +334,10 @@
   StringAttr emptyStringAttr;
 
 public:
-  MLIRContextImpl() : identifiers(identifierAllocator) {}
+  MLIRContextImpl() : identifiers(identifierAllocator) {
+    if (threadingIsEnabled)
+      threadPool.emplace();
+  }
   ~MLIRContextImpl() {
     for (auto typeMapping : registeredTypes)
       typeMapping.second->~AbstractType();
@@ -573,12 +576,19 @@
   impl->affineUniquer.disableMultithreading(disable);
   impl->attributeUniquer.disableMultithreading(disable);
   impl->typeUniquer.disableMultithreading(disable);
+
+  // Destroy thread pool (stop all threads) if it is no longer needed, or create
+  // a new one if multithreading was re-enabled.
+  if (!impl->threadingIsEnabled)
+    impl->threadPool.reset();
+  else if (!impl->threadPool.hasValue())
+    impl->threadPool.emplace();
 }
 
 llvm::ThreadPool &MLIRContext::getThreadPool() {
   assert(isMultithreadingEnabled() &&
          "expected multi-threading to be enabled within the context");
-  return impl->threadPool;
+  return *impl->threadPool;
 }
 
 void MLIRContext::enterMultiThreadedExecution() {