diff --git a/changelog.d/10775.misc b/changelog.d/10775.misc
new file mode 100644
index 000000000..ca87d7aed
--- /dev/null
+++ b/changelog.d/10775.misc
@@ -0,0 +1 @@
+Add a constant for `m.federate`.
diff --git a/synapse/api/constants.py b/synapse/api/constants.py
index 5f0f34119..236f0c7f9 100644
--- a/synapse/api/constants.py
+++ b/synapse/api/constants.py
@@ -198,6 +198,9 @@ class EventContentFields:
     # cf https://github.com/matrix-org/matrix-doc/pull/1772
     ROOM_TYPE = "type"
 
+    # Whether a room can federate.
+    FEDERATE = "m.federate"
+
     # The creator of the room, as used in `m.room.create` events.
     ROOM_CREATOR = "creator"
 
diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index b63a1afe9..cb133f3f8 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -21,7 +21,13 @@ from signedjson.key import decode_verify_key_bytes
 from signedjson.sign import SignatureVerifyException, verify_signed_json
 from unpaddedbase64 import decode_base64
 
-from synapse.api.constants import MAX_PDU_SIZE, EventTypes, JoinRules, Membership
+from synapse.api.constants import (
+    MAX_PDU_SIZE,
+    EventContentFields,
+    EventTypes,
+    JoinRules,
+    Membership,
+)
 from synapse.api.errors import AuthError, EventSizeError, SynapseError
 from synapse.api.room_versions import (
     KNOWN_ROOM_VERSIONS,
@@ -236,7 +242,7 @@ def _can_federate(event: EventBase, auth_events: StateMap[EventBase]) -> bool:
     if not creation_event:
         return False
 
-    return creation_event.content.get("m.federate", True) is True
+    return creation_event.content.get(EventContentFields.FEDERATE, True) is True
 
 
 def _is_membership_change_allowed(
diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py
index 0ed59d757..c374a1fbc 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -21,7 +21,13 @@ from prometheus_client import Counter
 from typing_extensions import TypedDict
 
 from synapse import types
-from synapse.api.constants import MAX_USERID_LENGTH, EventTypes, JoinRules, LoginType
+from synapse.api.constants import (
+    MAX_USERID_LENGTH,
+    EventContentFields,
+    EventTypes,
+    JoinRules,
+    LoginType,
+)
 from synapse.api.errors import AuthError, Codes, ConsentNotGivenError, SynapseError
 from synapse.appservice import ApplicationService
 from synapse.config.server import is_threepid_reserved
@@ -405,7 +411,7 @@ class RegistrationHandler(BaseHandler):
 
         # Choose whether to federate the new room.
         if not self.hs.config.registration.autocreate_auto_join_rooms_federated:
-            stub_config["creation_content"] = {"m.federate": False}
+            stub_config["creation_content"] = {EventContentFields.FEDERATE: False}
 
         for r in self.hs.config.registration.auto_join_rooms:
             logger.info("Auto-joining %s to %s", user_id, r)
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 0235fd09b..2932ed8a9 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -390,9 +390,9 @@ class RoomCreationHandler(BaseHandler):
         old_room_create_event = await self.store.get_create_event_for_room(old_room_id)
 
         # Check if the create event specified a non-federatable room
-        if not old_room_create_event.content.get("m.federate", True):
+        if not old_room_create_event.content.get(EventContentFields.FEDERATE, True):
             # If so, mark the new room as non-federatable as well
-            creation_content["m.federate"] = False
+            creation_content[EventContentFields.FEDERATE] = False
 
         initial_state = {}
 
diff --git a/synapse/handlers/room_list.py b/synapse/handlers/room_list.py
index 92bb75c84..81680b8df 100644
--- a/synapse/handlers/room_list.py
+++ b/synapse/handlers/room_list.py
@@ -313,7 +313,9 @@ class RoomListHandler(BaseHandler):
 
         # Return whether this room is open to federation users or not
         create_event = current_state[EventTypes.Create, ""]
-        result["m.federate"] = create_event.content.get("m.federate", True)
+        result["m.federate"] = create_event.content.get(
+            EventContentFields.FEDERATE, True
+        )
 
         name_event = current_state.get((EventTypes.Name, ""))
         if name_event:
diff --git a/synapse/handlers/stats.py b/synapse/handlers/stats.py
index 3a4c41c9f..47f2e2a0c 100644
--- a/synapse/handlers/stats.py
+++ b/synapse/handlers/stats.py
@@ -254,7 +254,7 @@ class StatsHandler:
 
             elif typ == EventTypes.Create:
                 room_state["is_federatable"] = (
-                    event_content.get("m.federate", True) is True
+                    event_content.get(EventContentFields.FEDERATE, True) is True
                 )
             elif typ == EventTypes.JoinRules:
                 room_state["join_rules"] = event_content.get("join_rule")
diff --git a/synapse/storage/databases/main/stats.py b/synapse/storage/databases/main/stats.py
index 42edbcc05..4245fa1a3 100644
--- a/synapse/storage/databases/main/stats.py
+++ b/synapse/storage/databases/main/stats.py
@@ -22,7 +22,7 @@ from typing_extensions import Counter
 
 from twisted.internet.defer import DeferredLock
 
-from synapse.api.constants import EventTypes, Membership
+from synapse.api.constants import EventContentFields, EventTypes, Membership
 from synapse.api.errors import StoreError
 from synapse.storage.database import DatabasePool
 from synapse.storage.databases.main.state_deltas import StateDeltasStore
@@ -590,7 +590,7 @@ class StatsStore(StateDeltasStore):
                 room_state["canonical_alias"] = event.content.get("alias")
             elif event.type == EventTypes.Create:
                 room_state["is_federatable"] = (
-                    event.content.get("m.federate", True) is True
+                    event.content.get(EventContentFields.FEDERATE, True) is True
                 )
 
         await self.update_room_state(room_id, room_state)