diff --git a/changelog.d/7506.feature b/changelog.d/7506.feature
new file mode 100644
index 0000000000000000000000000000000000000000..1407c91689617daae44d8a08217b68f397f9149d
--- /dev/null
+++ b/changelog.d/7506.feature
@@ -0,0 +1 @@
+Implement room version 6 per [MSC2240](https://github.com/matrix-org/matrix-doc/pull/2240).
diff --git a/synapse/api/room_versions.py b/synapse/api/room_versions.py
index 0901afb900dfefc090c6e0672312ee234bd4b2dd..d7baf2bc3989e9750012d420a64263956e5b0efc 100644
--- a/synapse/api/room_versions.py
+++ b/synapse/api/room_versions.py
@@ -120,34 +120,14 @@ class RoomVersions(object):
         strict_canonicaljson=False,
         limit_notifications_power_levels=False,
     )
-    MSC2432_DEV = RoomVersion(
-        "org.matrix.msc2432",
-        RoomDisposition.UNSTABLE,
+    V6 = RoomVersion(
+        "6",
+        RoomDisposition.STABLE,
         EventFormatVersions.V3,
         StateResolutionVersions.V2,
         enforce_key_validity=True,
         special_case_aliases_auth=False,
-        strict_canonicaljson=False,
-        limit_notifications_power_levels=False,
-    )
-    STRICT_CANONICALJSON = RoomVersion(
-        "org.matrix.strict_canonicaljson",
-        RoomDisposition.UNSTABLE,
-        EventFormatVersions.V3,
-        StateResolutionVersions.V2,
-        enforce_key_validity=True,
-        special_case_aliases_auth=True,
         strict_canonicaljson=True,
-        limit_notifications_power_levels=False,
-    )
-    MSC2209_DEV = RoomVersion(
-        "org.matrix.msc2209",
-        RoomDisposition.UNSTABLE,
-        EventFormatVersions.V3,
-        StateResolutionVersions.V2,
-        enforce_key_validity=True,
-        special_case_aliases_auth=True,
-        strict_canonicaljson=False,
         limit_notifications_power_levels=True,
     )
 
@@ -160,8 +140,6 @@ KNOWN_ROOM_VERSIONS = {
         RoomVersions.V3,
         RoomVersions.V4,
         RoomVersions.V5,
-        RoomVersions.MSC2432_DEV,
-        RoomVersions.STRICT_CANONICALJSON,
-        RoomVersions.MSC2209_DEV,
+        RoomVersions.V6,
     )
 }  # type: Dict[str, RoomVersion]
diff --git a/tests/events/test_utils.py b/tests/events/test_utils.py
index ab5f5ac54963fdf4cdff69b55e10c5cfb63d5426..c1274c14af59cdea131c7ee1507f2cb73a76c88c 100644
--- a/tests/events/test_utils.py
+++ b/tests/events/test_utils.py
@@ -156,7 +156,7 @@ class PruneEventTestCase(unittest.TestCase):
                 "signatures": {},
                 "unsigned": {},
             },
-            room_version=RoomVersions.MSC2432_DEV,
+            room_version=RoomVersions.V6,
         )
 
 
diff --git a/tests/handlers/test_federation.py b/tests/handlers/test_federation.py
index dfef58e704747591a02a897b88a5faa968c28894..96fea586730961f6f59dc17240cd4c9be2c0d335 100644
--- a/tests/handlers/test_federation.py
+++ b/tests/handlers/test_federation.py
@@ -226,7 +226,7 @@ class EventFromPduTestCase(TestCase):
                 "auth_events": [],
                 "origin_server_ts": 1234,
             },
-            RoomVersions.STRICT_CANONICALJSON,
+            RoomVersions.V6,
         )
 
         self.assertIsInstance(ev, EventBase)
@@ -253,7 +253,7 @@ class EventFromPduTestCase(TestCase):
                         "auth_events": [],
                         "origin_server_ts": 1234,
                     },
-                    RoomVersions.STRICT_CANONICALJSON,
+                    RoomVersions.V6,
                 )
 
     def test_invalid_nested(self):
@@ -270,5 +270,5 @@ class EventFromPduTestCase(TestCase):
                     "auth_events": [],
                     "origin_server_ts": 1234,
                 },
-                RoomVersions.STRICT_CANONICALJSON,
+                RoomVersions.V6,
             )
diff --git a/tests/test_event_auth.py b/tests/test_event_auth.py
index f2def601fb29b99c9fed2ac169fd998a73f76d2a..69b4c5d6c2f9a526b769a713e91b7b59e7573472 100644
--- a/tests/test_event_auth.py
+++ b/tests/test_event_auth.py
@@ -136,21 +136,18 @@ class EventAuthTestCase(unittest.TestCase):
 
         # creator should be able to send aliases
         event_auth.check(
-            RoomVersions.MSC2432_DEV,
-            _alias_event(creator),
-            auth_events,
-            do_sig_check=False,
+            RoomVersions.V6, _alias_event(creator), auth_events, do_sig_check=False,
         )
 
         # No particular checks are done on the state key.
         event_auth.check(
-            RoomVersions.MSC2432_DEV,
+            RoomVersions.V6,
             _alias_event(creator, state_key=""),
             auth_events,
             do_sig_check=False,
         )
         event_auth.check(
-            RoomVersions.MSC2432_DEV,
+            RoomVersions.V6,
             _alias_event(creator, state_key="test.com"),
             auth_events,
             do_sig_check=False,
@@ -159,10 +156,7 @@ class EventAuthTestCase(unittest.TestCase):
         # Per standard auth rules, the member must be in the room.
         with self.assertRaises(AuthError):
             event_auth.check(
-                RoomVersions.MSC2432_DEV,
-                _alias_event(other),
-                auth_events,
-                do_sig_check=False,
+                RoomVersions.V6, _alias_event(other), auth_events, do_sig_check=False,
             )
 
     def test_msc2209(self):
@@ -192,7 +186,7 @@ class EventAuthTestCase(unittest.TestCase):
         # But an MSC2209 room rejects this change.
         with self.assertRaises(AuthError):
             event_auth.check(
-                RoomVersions.MSC2209_DEV,
+                RoomVersions.V6,
                 _power_levels_event(pleb, {"notifications": {"room": 100}}),
                 auth_events,
                 do_sig_check=False,