diff --git a/changes/21148 b/changes/21148
new file mode 100644
index 0000000000..4e3c332279
--- /dev/null
+++ b/changes/21148
@@ -0,0 +1,4 @@
+  o Documentation:
+    - Restore documentation for the authorities' "approved-routers" file.
+      Closes ticket 21148.
+
diff --git a/doc/tor.1.txt b/doc/tor.1.txt
index 03af9c4be8..85af8c3a3d 100644
--- a/doc/tor.1.txt
+++ b/doc/tor.1.txt
@@ -2868,6 +2868,16 @@ __DataDirectory__**/hashed-fingerprint**::
     Only used by bridges. Holds the hashed fingerprint of the bridge's
     identity key. (That is, the hash of the hash of the identity key.)
 
+__DataDirectory__**/approved-routers**::
+    Only used by authoritative directory servers. This file lists
+    the status of routers by their identity fingerprint.
+    Each line lists a status and a fingerprint separated by
+    whitespace. See your **fingerprint** file in the __DataDirectory__ for an
+    example line. If the status is **!reject** then descriptors from the
+    given identity (fingerprint) are rejected by this server. If it is
+    **!invalid** then descriptors are accepted but marked in the directory as
+    not valid, that is, not recommended.
+
 __DataDirectory__**/v3-status-votes**::
     Only for v3 authoritative directory servers. This file contains
     status votes from all the authoritative directory servers.