diff --git a/changelog.d/16178.doc b/changelog.d/16178.doc
new file mode 100644
index 0000000000..ea21e19240
--- /dev/null
+++ b/changelog.d/16178.doc
@@ -0,0 +1 @@
+Document `exclude_rooms_from_sync` configuration option.
diff --git a/docs/usage/configuration/config_documentation.md b/docs/usage/configuration/config_documentation.md
index 235f873860..0b1725816e 100644
--- a/docs/usage/configuration/config_documentation.md
+++ b/docs/usage/configuration/config_documentation.md
@@ -3867,6 +3867,19 @@ Example configuration:
 ```yaml
 forget_rooms_on_leave: false
 ```
+---
+### `exclude_rooms_from_sync`
+A list of rooms to exclude from sync responses. This is useful for server
+administrators wishing to group users into a room without these users being able
+to see it from their client.
+
+By default, no room is excluded.
+
+Example configuration:
+```yaml
+exclude_rooms_from_sync:
+    - !foo:example.com
+```
 
 ---
 ## Opentracing