diff --git a/changelog.d/18133.misc b/changelog.d/18133.misc
new file mode 100644
index 000000000..151ceb2ca
--- /dev/null
+++ b/changelog.d/18133.misc
@@ -0,0 +1 @@
+Disable statement timeout during room purge.
diff --git a/synapse/storage/databases/state/store.py b/synapse/storage/databases/state/store.py
index 90d7beb92..c1a66dcba 100644
--- a/synapse/storage/databases/state/store.py
+++ b/synapse/storage/databases/state/store.py
@@ -48,6 +48,7 @@ from synapse.storage.database import (
     LoggingTransaction,
 )
 from synapse.storage.databases.state.bg_updates import StateBackgroundUpdateStore
+from synapse.storage.engines import PostgresEngine
 from synapse.storage.types import Cursor
 from synapse.storage.util.sequence import build_sequence_generator
 from synapse.types import MutableStateMap, StateKey, StateMap
@@ -914,6 +915,12 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
     ) -> None:
         # Delete all edges that reference a state group linked to room_id
         logger.info("[purge] removing %s from state_group_edges", room_id)
+
+        if isinstance(self.database_engine, PostgresEngine):
+            # Disable statement timeouts for this transaction; purging rooms can
+            # take a while!
+            txn.execute("SET LOCAL statement_timeout = 0")
+
         txn.execute(
             """
             DELETE FROM state_group_edges AS sge WHERE sge.state_group IN (