diff --git a/CHANGES.md b/CHANGES.md
index dfdd8aa68a..dec2630130 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,16 @@
+Synapse 1.21.0 (2020-10-12)
+===========================
+
+No significant changes since v1.21.0rc3.
+
+As [noted in
+v1.20.0](https://github.com/matrix-org/synapse/blob/release-v1.21.0/CHANGES.md#synapse-1200-2020-09-22),
+a future release will drop support for accessing Synapse's
+[Admin API](https://github.com/matrix-org/synapse/tree/master/docs/admin_api) under the
+`/_matrix/client/*` endpoint prefixes. At that point, the Admin API will only
+be accessible under `/_synapse/admin`.
+
+
 Synapse 1.21.0rc3 (2020-10-08)
 ==============================
 
@@ -154,9 +167,11 @@ API](https://github.com/matrix-org/synapse/tree/master/docs) has been
 accessible under the `/_matrix/client/api/v1/admin`,
 `/_matrix/client/unstable/admin`, `/_matrix/client/r0/admin` and
 `/_synapse/admin` prefixes. In a future release, we will be dropping support
-for accessing Synapse's Admin API using the `/_matrix/client/*` prefixes. This
-makes it easier for homeserver admins to lock down external access to the Admin
-API endpoints.
+for accessing Synapse's Admin API using the `/_matrix/client/*` prefixes.
+
+From that point, the Admin API will only be accessible under `/_synapse/admin`.
+This makes it easier for homeserver admins to lock down external access to the
+Admin API endpoints.
 
 Synapse 1.20.0rc5 (2020-09-18)
 ==============================
diff --git a/debian/changelog b/debian/changelog
index 264ef9ce7c..a08782f587 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,9 @@
+matrix-synapse-py3 (1.21.0) stable; urgency=medium
+
+  * New synapse release 1.21.0.
+
+ -- Synapse Packaging team <packages@matrix.org>  Mon, 12 Oct 2020 15:47:44 +0100
+
 matrix-synapse-py3 (1.20.1) stable; urgency=medium
 
   * New synapse release 1.20.1.
diff --git a/synapse/__init__.py b/synapse/__init__.py
index a86dc07ddc..57f818125a 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -48,7 +48,7 @@ try:
 except ImportError:
     pass
 
-__version__ = "1.21.0rc3"
+__version__ = "1.21.0"
 
 if bool(os.environ.get("SYNAPSE_TEST_PATCH_LOG_CONTEXTS", False)):
     # We import here so that we don't have to install a bunch of deps when