diff --git a/changelog.d/6682.bugfix b/changelog.d/6682.bugfix
new file mode 100644
index 000000000..d48ea3147
--- /dev/null
+++ b/changelog.d/6682.bugfix
@@ -0,0 +1,2 @@
+Fix "CRITICAL" errors being logged when a request is received for a uri containing non-ascii characters.
+
diff --git a/synapse/http/site.py b/synapse/http/site.py
index 9f2d035fa..911251c0b 100644
--- a/synapse/http/site.py
+++ b/synapse/http/site.py
@@ -88,7 +88,7 @@ class SynapseRequest(Request):
     def get_redacted_uri(self):
         uri = self.uri
         if isinstance(uri, bytes):
-            uri = self.uri.decode("ascii")
+            uri = self.uri.decode("ascii", errors="replace")
         return redact_uri(uri)
 
     def get_method(self):