diff --git a/datasette/app.py b/datasette/app.py
index f9bf91a8..54cf02f8 100644
--- a/datasette/app.py
+++ b/datasette/app.py
@@ -1,4 +1,5 @@
 import asyncio
+import asgi_csrf
 import collections
 import datetime
 import hashlib
@@ -884,7 +885,14 @@ class Datasette:
                     await database.table_counts(limit=60 * 60 * 1000)
 
         asgi = AsgiLifespan(
-            AsgiTracer(DatasetteRouter(self, routes)), on_startup=setup_db
+            AsgiTracer(
+                asgi_csrf.asgi_csrf(
+                    DatasetteRouter(self, routes),
+                    signing_secret=self._secret,
+                    cookie_name="ds_csrftoken",
+                )
+            ),
+            on_startup=setup_db,
         )
         for wrapper in pm.hook.asgi_wrapper(datasette=self):
             asgi = wrapper(asgi)
diff --git a/datasette/templates/messages_debug.html b/datasette/templates/messages_debug.html
index b2e1bc7c..e83d2a2f 100644
--- a/datasette/templates/messages_debug.html
+++ b/datasette/templates/messages_debug.html
@@ -8,7 +8,7 @@
 
 <p>Set a message:</p>
 
-<form action="/-/messages" method="POST">
+<form action="/-/messages" method="post">
     <div>
         <input type="text" name="message" style="width: 40%">
         <div class="select-wrapper">
@@ -19,6 +19,7 @@
                 <option>all</option>
             </select>
         </div>
+        <input type="hidden" name="csrftoken" value="{{ csrftoken() }}">
         <input type="submit" value="Add message">
     </div>
 </form>
diff --git a/datasette/templates/query.html b/datasette/templates/query.html
index 52896e96..a7cb6647 100644
--- a/datasette/templates/query.html
+++ b/datasette/templates/query.html
@@ -52,6 +52,7 @@
     {% endif %}
     <p>
         <button id="sql-format" type="button" hidden>Format SQL</button>
+        {% if canned_query %}<input type="hidden" name="csrftoken" value="{{ csrftoken() }}">{% endif %}
         <input type="submit" value="Run SQL">
     </p>
 </form>
diff --git a/datasette/utils/__init__.py b/datasette/utils/__init__.py
index 69e288e6..059db184 100644
--- a/datasette/utils/__init__.py
+++ b/datasette/utils/__init__.py
@@ -772,6 +772,9 @@ class MultiParams:
                 new_data.setdefault(key, []).append(value)
             self._data = new_data
 
+    def __repr__(self):
+        return "<MultiParams: {}>".format(self._data)
+
     def __contains__(self, key):
         return key in self._data
 
diff --git a/datasette/views/base.py b/datasette/views/base.py
index 2402406a..315c96fe 100644
--- a/datasette/views/base.py
+++ b/datasette/views/base.py
@@ -95,6 +95,7 @@ class BaseView(AsgiView):
             **context,
             **{
                 "database_url": self.database_url,
+                "csrftoken": request.scope["csrftoken"],
                 "database_color": self.database_color,
                 "show_messages": lambda: self.ds._show_messages(request),
                 "select_templates": [
diff --git a/setup.py b/setup.py
index 93628266..c0316deb 100644
--- a/setup.py
+++ b/setup.py
@@ -53,6 +53,7 @@ setup(
         "uvicorn~=0.11",
         "aiofiles>=0.4,<0.6",
         "janus>=0.4,<0.6",
+        "asgi-csrf>=0.4",
         "PyYAML~=5.3",
         "mergedeep>=1.1.1,<1.4.0",
         "itsdangerous~=1.1",
diff --git a/tests/fixtures.py b/tests/fixtures.py
index 78a54c68..a64a8295 100644
--- a/tests/fixtures.py
+++ b/tests/fixtures.py
@@ -1,5 +1,5 @@
 from datasette.app import Datasette
-from datasette.utils import sqlite3
+from datasette.utils import sqlite3, MultiParams
 from asgiref.testing import ApplicationCommunicator
 from asgiref.sync import async_to_sync
 from http.cookies import SimpleCookie
@@ -60,10 +60,35 @@ class TestClient:
 
     @async_to_sync
     async def post(
-        self, path, post_data=None, allow_redirects=True, redirect_count=0, cookies=None
+        self,
+        path,
+        post_data=None,
+        allow_redirects=True,
+        redirect_count=0,
+        content_type="application/x-www-form-urlencoded",
+        cookies=None,
+        csrftoken_from=None,
     ):
+        cookies = cookies or {}
+        post_data = post_data or {}
+        # Maybe fetch a csrftoken first
+        if csrftoken_from is not None:
+            if csrftoken_from is True:
+                csrftoken_from = path
+            token_response = await self._request(csrftoken_from)
+            # Check this had a Vary: Cookie header
+            assert "Cookie" == token_response.headers["vary"]
+            csrftoken = token_response.cookies["ds_csrftoken"]
+            cookies["ds_csrftoken"] = csrftoken
+            post_data["csrftoken"] = csrftoken
         return await self._request(
-            path, allow_redirects, redirect_count, "POST", cookies, post_data
+            path,
+            allow_redirects,
+            redirect_count,
+            "POST",
+            cookies,
+            post_data,
+            content_type,
         )
 
     async def _request(
@@ -74,6 +99,7 @@ class TestClient:
         method="GET",
         cookies=None,
         post_data=None,
+        content_type=None,
     ):
         query_string = b""
         if "?" in path:
@@ -84,6 +110,8 @@ class TestClient:
         else:
             raw_path = quote(path, safe="/:,").encode("latin-1")
         headers = [[b"host", b"localhost"]]
+        if content_type:
+            headers.append((b"content-type", content_type.encode("utf-8")))
         if cookies:
             sc = SimpleCookie()
             for key, value in cookies.items():
@@ -111,7 +139,7 @@ class TestClient:
         start = await instance.receive_output(2)
         messages.append(start)
         assert start["type"] == "http.response.start"
-        headers = dict(
+        response_headers = MultiParams(
             [(k.decode("utf8"), v.decode("utf8")) for k, v in start["headers"]]
         )
         status = start["status"]
@@ -124,7 +152,7 @@ class TestClient:
             body += message["body"]
             if not message.get("more_body"):
                 break
-        response = TestResponse(status, headers, body)
+        response = TestResponse(status, response_headers, body)
         if allow_redirects and response.status in (301, 302):
             assert (
                 redirect_count < self.max_redirects
diff --git a/tests/test_canned_write.py b/tests/test_canned_write.py
index 692d726e..be838063 100644
--- a/tests/test_canned_write.py
+++ b/tests/test_canned_write.py
@@ -40,7 +40,7 @@ def canned_write_client():
 
 def test_insert(canned_write_client):
     response = canned_write_client.post(
-        "/data/add_name", {"name": "Hello"}, allow_redirects=False
+        "/data/add_name", {"name": "Hello"}, allow_redirects=False, csrftoken_from=True,
     )
     assert 302 == response.status
     assert "/data/add_name?success" == response.headers["Location"]
@@ -52,7 +52,7 @@ def test_insert(canned_write_client):
 
 def test_custom_success_message(canned_write_client):
     response = canned_write_client.post(
-        "/data/delete_name", {"rowid": 1}, allow_redirects=False
+        "/data/delete_name", {"rowid": 1}, allow_redirects=False, csrftoken_from=True
     )
     assert 302 == response.status
     messages = canned_write_client.ds.unsign(
@@ -62,11 +62,12 @@ def test_custom_success_message(canned_write_client):
 
 
 def test_insert_error(canned_write_client):
-    canned_write_client.post("/data/add_name", {"name": "Hello"})
+    canned_write_client.post("/data/add_name", {"name": "Hello"}, csrftoken_from=True)
     response = canned_write_client.post(
         "/data/add_name_specify_id",
         {"rowid": 1, "name": "Should fail"},
         allow_redirects=False,
+        csrftoken_from=True,
     )
     assert 302 == response.status
     assert "/data/add_name_specify_id?error" == response.headers["Location"]
@@ -82,6 +83,7 @@ def test_insert_error(canned_write_client):
         "/data/add_name_specify_id",
         {"rowid": 1, "name": "Should fail"},
         allow_redirects=False,
+        csrftoken_from=True,
     )
     assert [["ERROR", 3]] == canned_write_client.ds.unsign(
         response.cookies["ds_messages"], "messages"
diff --git a/tests/test_utils.py b/tests/test_utils.py
index a7968e54..cf714215 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -439,15 +439,18 @@ def test_call_with_supported_arguments():
         utils.call_with_supported_arguments(foo, a=1)
 
 
-@pytest.mark.parametrize("data,should_raise", [
-    ([["foo", "bar"], ["foo", "baz"]], False),
-    ([("foo", "bar"), ("foo", "baz")], False),
-    ((["foo", "bar"], ["foo", "baz"]), False),
-    ([["foo", "bar"], ["foo", "baz", "bax"]], True),
-    ({"foo": ["bar", "baz"]}, False),
-    ({"foo": ("bar", "baz")}, False),
-    ({"foo": "bar"}, True),
-])
+@pytest.mark.parametrize(
+    "data,should_raise",
+    [
+        ([["foo", "bar"], ["foo", "baz"]], False),
+        ([("foo", "bar"), ("foo", "baz")], False),
+        ((["foo", "bar"], ["foo", "baz"]), False),
+        ([["foo", "bar"], ["foo", "baz", "bax"]], True),
+        ({"foo": ["bar", "baz"]}, False),
+        ({"foo": ("bar", "baz")}, False),
+        ({"foo": "bar"}, True),
+    ]
+)
 def test_multi_params(data, should_raise):
     if should_raise:
         with pytest.raises(AssertionError):