diff --git a/changelog.d/12845.feature b/changelog.d/12845.feature
new file mode 100644
index 0000000000..628fb16d08
--- /dev/null
+++ b/changelog.d/12845.feature
@@ -0,0 +1 @@
+Support the new error code "M_ORG_MATRIX_MSC3823_USER_ACCOUNT_SUSPENDED" from [MSC3823](https://github.com/matrix-org/matrix-spec-proposals/pull/3823).
\ No newline at end of file
diff --git a/synapse/api/errors.py b/synapse/api/errors.py
index 6650e826d5..05e96843cf 100644
--- a/synapse/api/errors.py
+++ b/synapse/api/errors.py
@@ -79,6 +79,13 @@ class Codes(str, Enum):
     WEAK_PASSWORD = "M_WEAK_PASSWORD"
     INVALID_SIGNATURE = "M_INVALID_SIGNATURE"
     USER_DEACTIVATED = "M_USER_DEACTIVATED"
+
+    # The account has been suspended on the server.
+    # By opposition to `USER_DEACTIVATED`, this is a reversible measure
+    # that can possibly be appealed and reverted.
+    # Part of MSC3823.
+    USER_ACCOUNT_SUSPENDED = "M_ORG_MATRIX_MSC3823_USER_ACCOUNT_SUSPENDED"
+
     BAD_ALIAS = "M_BAD_ALIAS"
     # For restricted join rules.
     UNABLE_AUTHORISE_JOIN = "M_UNABLE_TO_AUTHORISE_JOIN"