diff --git a/newsfragments/10.feature.rst b/newsfragments/10.feature.rst
new file mode 100644
index 0000000..1749fa0
--- /dev/null
+++ b/newsfragments/10.feature.rst
@@ -0,0 +1,3 @@
+Sniffio can now detect Twisted_.
+
+.. _Twisted: https://twistedmatrix.com/trac/
diff --git a/sniffio/_impl.py b/sniffio/_impl.py
index c1a7bbf..828debe 100644
--- a/sniffio/_impl.py
+++ b/sniffio/_impl.py
@@ -89,6 +89,13 @@ async def generic_sleep(seconds):
         from curio.meta import curio_running
         if curio_running():
             return 'curio'
+    
+    # Sniff for Twisted
+    if 'twisted' in sys.modules:
+        from twisted.internet import reactor
+        from twisted.python.threadable import isInIOThread
+        if reactor.running and isInIOThread():
+            return "twisted"
 
     raise AsyncLibraryNotFoundError(
         "unknown async library, or not in async context"
diff --git a/sniffio/_tests/test_sniffio.py b/sniffio/_tests/test_sniffio.py
index 984c8c0..59159e6 100644
--- a/sniffio/_tests/test_sniffio.py
+++ b/sniffio/_tests/test_sniffio.py
@@ -1,5 +1,6 @@
 import os
 import sys
+import warnings
 
 import pytest
 
@@ -82,3 +83,46 @@ async def this_is_curio():
 
     with pytest.raises(AsyncLibraryNotFoundError):
         current_async_library()
+
+
+@pytest.fixture(params=['select', 'asyncio'])
+def reactor(request):
+    with warnings.catch_warnings():
+        warnings.simplefilter('ignore', DeprecationWarning)
+        from twisted.internet import asyncioreactor, selectreactor
+
+    if request.param == 'asyncio':
+        import asyncio
+        loop = asyncio.new_event_loop()
+        asyncio.set_event_loop(loop)
+        asyncioreactor.install(loop)
+        yield
+        loop.close()
+    else:
+        selectreactor.install()
+        yield
+
+    del sys.modules['twisted.internet.reactor']
+
+
+def test_twisted(reactor):
+    from twisted.internet import reactor
+
+    with pytest.raises(AsyncLibraryNotFoundError):
+        current_async_library()
+
+    ran = []
+
+    def this_is_twisted():
+        try:
+            assert current_async_library() == "twisted"
+            ran.append(True)
+        finally:
+            reactor.stop()
+
+    reactor.callWhenRunning(this_is_twisted)
+    reactor.run()
+    assert ran == [True]
+
+    with pytest.raises(AsyncLibraryNotFoundError):
+        current_async_library()
diff --git a/test-requirements.txt b/test-requirements.txt
index 6742196..29af8d8 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,3 +1,4 @@
 pytest
 pytest-cov
 curio
+twisted