diff --git a/README.md b/README.md
index 42d67f8..be94d70 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,10 @@
 # Common Expression Language
 
+> [!WARNING]
+> **On June 16, 2026, this repository will move to [github.com/cel-expr/cel-spec](https://github.com/cel-expr/cel-spec)!**
+>
+> Please update your links and dependencies. See the [pinned issue](https://github.com/google/cel-spec/issues/513) for details.
+
 The Common Expression Language (CEL) implements common semantics for expression
 evaluation, enabling different applications to more easily interoperate.