diff --git a/google/cloud/alloydb/v1alpha/resources.proto b/google/cloud/alloydb/v1alpha/resources.proto
index 8fb7df7151..13f91f2d77 100644
--- a/google/cloud/alloydb/v1alpha/resources.proto
+++ b/google/cloud/alloydb/v1alpha/resources.proto
@@ -104,6 +104,9 @@ enum DatabaseVersion {
 
   // The database version is Postgres 17.
   POSTGRES_17 = 5;
+
+  // The database version is Postgres 18.
+  POSTGRES_18 = 6;
 }
 
 // Subscription_type added to distinguish between Standard and Trial