diff --git a/policy/action-constraint.go b/policy/action-constraint.go
new file mode 100644
index 00000000..4fae7493
--- /dev/null
+++ b/policy/action-constraint.go
@@ -0,0 +1,26 @@
+// Copyright (c) 2015-2026 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package policy
+
+// ActionType constrains the set of policy action types. It lets generic helpers
+// accept any typed action — S3 (Action), admin, STS, KMS, Tables, Vectors, or
+// Memory — without forcing callers to convert to Action at each call site. A
+// bare string is intentionally excluded so only real policy action types match.
+type ActionType interface {
+	Action | AdminAction | STSAction | KMSAction | TableAction | VectorsAction | MemoryAction
+}