diff --git a/keystone/conf/default.py b/keystone/conf/default.py
index 295597b82e..d72f00ccdd 100644
--- a/keystone/conf/default.py
+++ b/keystone/conf/default.py
@@ -59,6 +59,9 @@ adversely impact performance.
 max_param_size = cfg.IntOpt(
     'max_param_size',
     default=64,
+    deprecated_for_removal=True,
+    deprecated_reason=utils.fmt('This option has had no effect.'),
+    deprecated_since='2025.1',
     help=utils.fmt(
         """
 Limit the sizes of user & project ID/names.
diff --git a/releasenotes/notes/deprecate-max-param-size-6e0770e0c9d21dd6.yaml b/releasenotes/notes/deprecate-max-param-size-6e0770e0c9d21dd6.yaml
new file mode 100644
index 0000000000..eed1e8b175
--- /dev/null
+++ b/releasenotes/notes/deprecate-max-param-size-6e0770e0c9d21dd6.yaml
@@ -0,0 +1,6 @@
+---
+deprecations:
+  - |
+    The ``[DEFAULT] max_param_size`` option has been deprecated. This option
+    was used in identity v2 APU but identity v2 API was removed in 13.0.0
+    release.