diff --git a/.circleci/config.yml b/.circleci/config.yml
index 43a8a4ed..b366b894 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -64,6 +64,15 @@ jobs:
           command: |
             sudo pip install tox
             tox -e py39
+  py39-notrio:
+    docker:
+      - image: circleci/python:3.9
+    steps:
+      - checkout
+      - run:
+          command: |
+            sudo pip install tox
+            tox -e py39-notrio
   deploy:
     docker:
       - image: circleci/python:3.9
@@ -100,6 +109,7 @@ workflows:
       - py37
       - py38
       - py39
+      - py39-notrio
       - deploy:
           filters:
             tags:
diff --git a/doc/source/index.rst b/doc/source/index.rst
index 2f025ef1..02aa3e0f 100644
--- a/doc/source/index.rst
+++ b/doc/source/index.rst
@@ -546,28 +546,34 @@ With async code you can use AsyncRetrying.
 Async and retry
 ~~~~~~~~~~~~~~~
 
-Finally, ``retry`` works also on asyncio and Tornado (>= 4.5) coroutines.
+Finally, ``retry`` works also on asyncio, Trio, and Tornado (>= 4.5) coroutines.
 Sleeps are done asynchronously too.
 
 .. code-block:: python
 
     @retry
-    async def my_async_function(loop):
+    async def my_asyncio_function(loop):
         await loop.getaddrinfo('8.8.8.8', 53)
 
+.. code-block:: python
+
+    @retry
+    def my_async_trio_function():
+        await trio.socket.getaddrinfo('8.8.8.8', 53)
+
 .. code-block:: python
 
     @retry
     @tornado.gen.coroutine
-    def my_async_function(http_client, url):
+    def my_async_tornado_function(http_client, url):
         yield http_client.fetch(url)
 
-You can even use alternative event loops such as `curio` or `Trio` by passing the correct sleep function:
+You can even use alternative event loops such as `curio` by passing the correct sleep function:
 
 .. code-block:: python
 
-    @retry(sleep=trio.sleep)
-    async def my_async_function(loop):
+    @retry(sleep=curio.sleep)
+    async def my_async_curio_function():
         await asks.get('https://example.org')
 
 Contribute
diff --git a/releasenotes/notes/trio-support-62fed9e32ccb62be.yaml b/releasenotes/notes/trio-support-62fed9e32ccb62be.yaml
new file mode 100644
index 00000000..b8e0c149
--- /dev/null
+++ b/releasenotes/notes/trio-support-62fed9e32ccb62be.yaml
@@ -0,0 +1,6 @@
+---
+features:
+  - |
+    If you're using `Trio <https://trio.readthedocs.io>`__, then
+    ``@retry`` now works automatically. It's no longer necessary to
+    pass ``sleep=trio.sleep``.
diff --git a/tenacity/_asyncio.py b/tenacity/_asyncio.py
index 979b6544..55e9bf2b 100644
--- a/tenacity/_asyncio.py
+++ b/tenacity/_asyncio.py
@@ -16,7 +16,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import sys
-from asyncio import sleep
 
 from tenacity import AttemptManager
 from tenacity import BaseRetrying
@@ -25,8 +24,23 @@
 from tenacity import RetryCallState
 
 
+async def _portable_async_sleep(seconds):
+    # If trio is already imported, then importing it is cheap.
+    # If trio isn't already imported, then it's definitely not running, so we
+    # can skip further checks.
+    if "trio" in sys.modules:
+        # If trio is available, then sniffio is too
+        import trio, sniffio
+        if sniffio.current_async_library() == "trio":
+            await trio.sleep(seconds)
+            return
+    # Otherwise, assume asyncio
+    import asyncio
+    await asyncio.sleep(seconds)
+
+
 class AsyncRetrying(BaseRetrying):
-    def __init__(self, sleep=sleep, **kwargs):
+    def __init__(self, sleep=_portable_async_sleep, **kwargs):
         super(AsyncRetrying, self).__init__(**kwargs)
         self.sleep = sleep
 
diff --git a/tenacity/tests/test_asyncio.py b/tenacity/tests/test_asyncio.py
index 2057fd2d..c43a8e9e 100644
--- a/tenacity/tests/test_asyncio.py
+++ b/tenacity/tests/test_asyncio.py
@@ -17,6 +17,13 @@
 import inspect
 import unittest
 
+try:
+    import trio
+except ImportError:
+    have_trio = False
+else:
+    have_trio = True
+
 import pytest
 
 import six
@@ -54,7 +61,7 @@ async def _retryable_coroutine_with_2_attempts(thing):
     thing.go()
 
 
-class TestAsync(unittest.TestCase):
+class TestAsyncio(unittest.TestCase):
     @asynctest
     async def test_retry(self):
         thing = NoIOErrorAfterCount(5)
@@ -125,6 +132,21 @@ def after(retry_state):
         assert list(attempt_nos2) == [1, 2, 3]
 
 
+@unittest.skipIf(not have_trio, "trio not installed")
+class TestTrio(unittest.TestCase):
+    def test_trio_basic(self):
+        thing = NoIOErrorAfterCount(5)
+
+        @retry
+        async def trio_function():
+            await trio.sleep(0.00001)
+            return thing.go()
+
+        trio.run(trio_function)
+
+        assert thing.counter == thing.count
+
+
 class TestContextManager(unittest.TestCase):
     @asynctest
     async def test_do_max_attempts(self):
diff --git a/tox.ini b/tox.ini
index 20f3b12a..3414bbae 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py27, py35, py36, py37, py38, py39, pep8, pypy
+envlist = py27, py35, py36, py37, py38, py39, py39-trio, pep8, pypy
 
 [testenv]
 usedevelop = True
@@ -14,6 +14,14 @@ commands =
     py3{5,6,7,8,9}: sphinx-build -a -E -W -b doctest doc/source doc/build
     py3{5,6,7,8,9}: sphinx-build -a -E -W -b html doc/source doc/build
 
+[testenv:py39-trio]
+deps =
+    .[doc]
+    pytest
+    trio
+    typeguard;python_version>='3.0'
+commands = pytest {posargs}
+
 [testenv:pep8]
 basepython = python3
 deps = flake8