diff --git a/changelog.d/11318.feature b/changelog.d/11318.feature
new file mode 100644
index 000000000..ce28fc1ee
--- /dev/null
+++ b/changelog.d/11318.feature
@@ -0,0 +1 @@
+Add support for the `/_matrix/client/v3` APIs from Matrix v1.1.
\ No newline at end of file
diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index 7bb3744f0..4efadde57 100644
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -193,6 +193,7 @@ class SynapseHomeServer(HomeServer):
                 {
                     "/_matrix/client/api/v1": client_resource,
                     "/_matrix/client/r0": client_resource,
+                    "/_matrix/client/v3": client_resource,
                     "/_matrix/client/unstable": client_resource,
                     "/_matrix/client/v2_alpha": client_resource,
                     "/_matrix/client/versions": client_resource,
diff --git a/synapse/rest/client/_base.py b/synapse/rest/client/_base.py
index a0971ce99..b4cb90cb7 100644
--- a/synapse/rest/client/_base.py
+++ b/synapse/rest/client/_base.py
@@ -27,7 +27,7 @@ logger = logging.getLogger(__name__)
 
 def client_patterns(
     path_regex: str,
-    releases: Iterable[int] = (0,),
+    releases: Iterable[str] = ("r0", "v3"),
     unstable: bool = True,
     v1: bool = False,
 ) -> Iterable[Pattern]:
@@ -52,7 +52,7 @@ def client_patterns(
         v1_prefix = CLIENT_API_PREFIX + "/api/v1"
         patterns.append(re.compile("^" + v1_prefix + path_regex))
     for release in releases:
-        new_prefix = CLIENT_API_PREFIX + "/r%d" % (release,)
+        new_prefix = CLIENT_API_PREFIX + f"/{release}"
         patterns.append(re.compile("^" + new_prefix + path_regex))
 
     return patterns
diff --git a/synapse/rest/client/keys.py b/synapse/rest/client/keys.py
index 7281b2ee2..730c18f08 100644
--- a/synapse/rest/client/keys.py
+++ b/synapse/rest/client/keys.py
@@ -262,7 +262,7 @@ class SigningKeyUploadServlet(RestServlet):
     }
     """
 
-    PATTERNS = client_patterns("/keys/device_signing/upload$", releases=())
+    PATTERNS = client_patterns("/keys/device_signing/upload$", releases=("v3",))
 
     def __init__(self, hs: "HomeServer"):
         super().__init__()