diff --git a/src/Reactor/Coroutine.hpp b/src/Reactor/Coroutine.hpp
index d70ecf0..cd8763c 100644
--- a/src/Reactor/Coroutine.hpp
+++ b/src/Reactor/Coroutine.hpp
@@ -135,12 +135,10 @@
 	// executable code. After calling, no more reactor functions may be
 	// called without building a new rr::Function or rr::Coroutine.
 	// While automatically called by operator(), finalize() should be called
-	// as early as possible to release the global Reactor mutex lock.
-	// It must also be called explicitly on the same thread that instantiates
-	// the Coroutine instance if operator() is invoked on separate threads.
-	// This is because presently, Reactor backends use a global mutex scoped
-	// to the generation of routines, and these must be locked/unlocked on the
-	// same thread.
+	// as soon as possible once the coroutine has been fully built.
+	// finalize() *must* be called explicitly on the same thread that
+	// instantiates the Coroutine instance if operator() is to be invoked on
+	// different threads.
 	inline void finalize(const Config::Edit &cfg = Config::Edit::None);
 
 	// Starts execution of the coroutine and returns a unique_ptr to a
diff --git a/src/Reactor/LLVMJIT.cpp b/src/Reactor/LLVMJIT.cpp
index bbd91e3..68153a7 100644
--- a/src/Reactor/LLVMJIT.cpp
+++ b/src/Reactor/LLVMJIT.cpp
@@ -57,6 +57,7 @@
     __pragma(warning(pop))
 #endif
 
+#include <atomic>
 #include <unordered_map>
 
 #if defined(_WIN64)
@@ -610,7 +611,7 @@
 		for(size_t i = 0; i < count; i++)
 		{
 			auto func = funcs[i];
-			static size_t numEmittedFunctions = 0;
+			static std::atomic<size_t> numEmittedFunctions = { 0 };
 			std::string name = "f" + llvm::Twine(numEmittedFunctions++).str();
 			func->setName(name);
 			func->setLinkage(llvm::GlobalValue::ExternalLinkage);
diff --git a/src/Reactor/LLVMReactor.cpp b/src/Reactor/LLVMReactor.cpp
index 6cce3f2..48861e9 100644
--- a/src/Reactor/LLVMReactor.cpp
+++ b/src/Reactor/LLVMReactor.cpp
@@ -59,10 +59,13 @@
 }
 #endif
 
+#if !LLVM_ENABLE_THREADS
+#	error "LLVM_ENABLE_THREADS needs to be enabled"
+#endif
+
 namespace {
 
-std::unique_ptr<rr::JITBuilder> jit;
-std::mutex codegenMutex;
+thread_local std::unique_ptr<rr::JITBuilder> jit;
 
 // Default configuration settings. Must be accessed under mutex lock.
 std::mutex defaultConfigLock;
@@ -599,8 +602,6 @@
 
 Nucleus::Nucleus()
 {
-	::codegenMutex.lock();  // Reactor and LLVM are currently not thread safe
-
 	ASSERT(jit == nullptr);
 	jit.reset(new JITBuilder(Nucleus::getDefaultConfig()));
 }
@@ -608,7 +609,6 @@
 Nucleus::~Nucleus()
 {
 	jit.reset();
-	::codegenMutex.unlock();
 }
 
 void Nucleus::setDefaultConfig(const Config &cfg)
diff --git a/src/Reactor/Reactor.cpp b/src/Reactor/Reactor.cpp
index dff1a29..2bf5324 100644
--- a/src/Reactor/Reactor.cpp
+++ b/src/Reactor/Reactor.cpp
@@ -63,7 +63,7 @@
 }
 
 // Set of variables that do not have a stack location yet.
-std::unordered_set<Variable *> Variable::unmaterializedVariables;
+thread_local std::unordered_set<Variable *> Variable::unmaterializedVariables;
 
 Variable::Variable(Type *type, int arraySize)
     : arraySize(arraySize)
diff --git a/src/Reactor/Reactor.hpp b/src/Reactor/Reactor.hpp
index 488c0be..33e8b44 100644
--- a/src/Reactor/Reactor.hpp
+++ b/src/Reactor/Reactor.hpp
@@ -133,7 +133,7 @@
 	static void materializeAll();
 	static void killUnmaterialized();
 
-	static std::unordered_set<Variable *> unmaterializedVariables;
+	static thread_local std::unordered_set<Variable *> unmaterializedVariables;
 
 	Type *const type;
 	mutable Value *rvalue = nullptr;
diff --git a/src/Reactor/ReactorUnitTests.cpp b/src/Reactor/ReactorUnitTests.cpp
index d5aafa9..adb0cb4 100644
--- a/src/Reactor/ReactorUnitTests.cpp
+++ b/src/Reactor/ReactorUnitTests.cpp
@@ -2949,6 +2949,114 @@
 	EXPECT_EQ(result, value);
 }
 
+TEST(ReactorUnitTests, Multithreaded_Function)
+{
+	constexpr int numThreads = 32;
+	constexpr int numLoops = 64;
+
+	auto threads = std::unique_ptr<std::thread[]>(new std::thread[numThreads]);
+	auto results = std::unique_ptr<int[]>(new int[numThreads * numLoops]);
+
+	for(int t = 0; t < numThreads; t++)
+	{
+		auto threadFunc = [&](int t) {
+			for(int l = 0; l < numLoops; l++)
+			{
+				FunctionT<int(int, int)> function;
+				{
+					Int a = function.Arg<0>();
+					Int b = function.Arg<1>();
+					Return((a << 16) | b);
+				}
+
+				auto f = function("thread%d_loop%d", t, l);
+				results[t * numLoops + l] = f(t, l);
+			}
+		};
+		threads[t] = std::thread(threadFunc, t);
+	}
+
+	for(int t = 0; t < numThreads; t++)
+	{
+		threads[t].join();
+	}
+
+	for(int t = 0; t < numThreads; t++)
+	{
+		for(int l = 0; l < numLoops; l++)
+		{
+			auto expect = (t << 16) | l;
+			auto result = results[t * numLoops + l];
+			EXPECT_EQ(result, expect);
+		}
+	}
+}
+
+TEST(ReactorUnitTests, Multithreaded_Coroutine)
+{
+	if(!rr::Caps.CoroutinesSupported)
+	{
+		SUCCEED() << "Coroutines not supported";
+		return;
+	}
+
+	constexpr int numThreads = 32;
+	constexpr int numLoops = 64;
+
+	struct Result
+	{
+		bool yieldReturns[3];
+		int yieldValues[3];
+	};
+
+	auto threads = std::unique_ptr<std::thread[]>(new std::thread[numThreads]);
+	auto results = std::unique_ptr<Result[]>(new Result[numThreads * numLoops]);
+
+	for(int t = 0; t < numThreads; t++)
+	{
+		auto threadFunc = [&](int t) {
+			for(int l = 0; l < numLoops; l++)
+			{
+				Coroutine<int(int, int)> function;
+				{
+					Int a = function.Arg<0>();
+					Int b = function.Arg<1>();
+					Yield(a);
+					Yield(b);
+				}
+
+				auto coroutine = function(t, l);
+
+				auto &result = results[t * numLoops + l];
+				result = {};
+				result.yieldReturns[0] = coroutine->await(result.yieldValues[0]);
+				result.yieldReturns[1] = coroutine->await(result.yieldValues[1]);
+				result.yieldReturns[2] = coroutine->await(result.yieldValues[2]);
+			}
+		};
+		threads[t] = std::thread(threadFunc, t);
+	}
+
+	for(int t = 0; t < numThreads; t++)
+	{
+		threads[t].join();
+	}
+
+	for(int t = 0; t < numThreads; t++)
+	{
+		for(int l = 0; l < numLoops; l++)
+		{
+			auto const &result = results[t * numLoops + l];
+			EXPECT_EQ(result.yieldReturns[0], true);
+			EXPECT_EQ(result.yieldValues[0], t);
+			EXPECT_EQ(result.yieldReturns[1], true);
+			EXPECT_EQ(result.yieldValues[1], l);
+			EXPECT_EQ(result.yieldReturns[2], false);
+			EXPECT_EQ(result.yieldValues[2], 0);
+		}
+	}
+}
+
 int main(int argc, char **argv)
 {
 	::testing::InitGoogleTest(&argc, argv);