diff --git a/changelog.d/18722.feature b/changelog.d/18722.feature
new file mode 100644
index 00000000000..4a3cf4839a9
--- /dev/null
+++ b/changelog.d/18722.feature
@@ -0,0 +1 @@
+Advertise experimental support for [MSC4306](https://github.com/matrix-org/matrix-spec-proposals/pull/4306) through `/_matrix/clients/versions` if enabled.
diff --git a/synapse/rest/client/versions.py b/synapse/rest/client/versions.py
index fa39eb9e6d9..7f783795341 100644
--- a/synapse/rest/client/versions.py
+++ b/synapse/rest/client/versions.py
@@ -177,6 +177,8 @@ async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
                     "uk.tcpip.msc4133": self.config.experimental.msc4133_enabled,
                     # MSC4155: Invite filtering
                     "org.matrix.msc4155": self.config.experimental.msc4155_enabled,
+                    # MSC4306: Support for thread subscriptions
+                    "org.matrix.msc4306": self.config.experimental.msc4306_enabled,
                 },
             },
         )