diff --git a/changelog.d/8843.feature b/changelog.d/8843.feature
new file mode 100644
index 0000000000..824d46d5aa
--- /dev/null
+++ b/changelog.d/8843.feature
@@ -0,0 +1 @@
+Add `force_purge` option to delete-room admin api.
diff --git a/docs/admin_api/rooms.md b/docs/admin_api/rooms.md
index 0c05b0ed55..004a802e17 100644
--- a/docs/admin_api/rooms.md
+++ b/docs/admin_api/rooms.md
@@ -382,7 +382,7 @@ the new room. Users on other servers will be unaffected.
 
 The API is:
 
-```json
+```
 POST /_synapse/admin/v1/rooms/<room_id>/delete
 ```
 
@@ -439,6 +439,10 @@ The following JSON body parameters are available:
             future attempts to join the room. Defaults to `false`.
 * `purge` - Optional. If set to `true`, it will remove all traces of the room from your database.
             Defaults to `true`.
+* `force_purge` - Optional, and ignored unless `purge` is `true`. If set to `true`, it
+  will force a purge to go ahead even if there are local users still in the room. Do not
+  use this unless a regular `purge` operation fails, as it could leave those users'
+  clients in a confused state.
 
 The JSON body must not be empty. The body must be at least `{}`.
 
diff --git a/synapse/handlers/pagination.py b/synapse/handlers/pagination.py
index 426b58da9e..5372753707 100644
--- a/synapse/handlers/pagination.py
+++ b/synapse/handlers/pagination.py
@@ -299,17 +299,22 @@ class PaginationHandler:
         """
         return self._purges_by_id.get(purge_id)
 
-    async def purge_room(self, room_id: str) -> None:
-        """Purge the given room from the database"""
+    async def purge_room(self, room_id: str, force: bool = False) -> None:
+        """Purge the given room from the database.
+
+        Args:
+            room_id: room to be purged
+            force: set true to skip checking for joined users.
+        """
         with await self.pagination_lock.write(room_id):
             # check we know about the room
             await self.store.get_room_version_id(room_id)
 
             # first check that we have no users in this room
-            joined = await self.store.is_host_joined(room_id, self._server_name)
-
-            if joined:
-                raise SynapseError(400, "Users are still joined to this room")
+            if not force:
+                joined = await self.store.is_host_joined(room_id, self._server_name)
+                if joined:
+                    raise SynapseError(400, "Users are still joined to this room")
 
             await self.storage.purge_events.purge_room(room_id)
 
diff --git a/synapse/rest/admin/rooms.py b/synapse/rest/admin/rooms.py
index 353151169a..25f89e4685 100644
--- a/synapse/rest/admin/rooms.py
+++ b/synapse/rest/admin/rooms.py
@@ -70,14 +70,18 @@ class ShutdownRoomRestServlet(RestServlet):
 
 
 class DeleteRoomRestServlet(RestServlet):
-    """Delete a room from server. It is a combination and improvement of
-    shut down and purge room.
+    """Delete a room from server.
+
+    It is a combination and improvement of shutdown and purge room.
+
     Shuts down a room by removing all local users from the room.
     Blocking all future invites and joins to the room is optional.
+
     If desired any local aliases will be repointed to a new room
-    created by `new_room_user_id` and kicked users will be auto
+    created by `new_room_user_id` and kicked users will be auto-
     joined to the new room.
-    It will remove all trace of a room from the database.
+
+    If 'purge' is true, it will remove all traces of a room from the database.
     """
 
     PATTERNS = admin_patterns("/rooms/(?P<room_id>[^/]+)/delete$")
@@ -110,6 +114,14 @@ class DeleteRoomRestServlet(RestServlet):
                 Codes.BAD_JSON,
             )
 
+        force_purge = content.get("force_purge", False)
+        if not isinstance(force_purge, bool):
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST,
+                "Param 'force_purge' must be a boolean, if given",
+                Codes.BAD_JSON,
+            )
+
         ret = await self.room_shutdown_handler.shutdown_room(
             room_id=room_id,
             new_room_user_id=content.get("new_room_user_id"),
@@ -121,7 +133,7 @@ class DeleteRoomRestServlet(RestServlet):
 
         # Purge room
         if purge:
-            await self.pagination_handler.purge_room(room_id)
+            await self.pagination_handler.purge_room(room_id, force=force_purge)
 
         return (200, ret)