diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -2268,6 +2268,7 @@
     'PhabricatorAuthChallengeStatusController' => 'applications/auth/controller/mfa/PhabricatorAuthChallengeStatusController.php',
     'PhabricatorAuthChallengeUpdate' => 'applications/auth/view/PhabricatorAuthChallengeUpdate.php',
     'PhabricatorAuthChangePasswordAction' => 'applications/auth/action/PhabricatorAuthChangePasswordAction.php',
+    'PhabricatorAuthChangeUsernameMessageType' => 'applications/auth/message/PhabricatorAuthChangeUsernameMessageType.php',
     'PhabricatorAuthConduitAPIMethod' => 'applications/auth/conduit/PhabricatorAuthConduitAPIMethod.php',
     'PhabricatorAuthConduitTokenRevoker' => 'applications/auth/revoker/PhabricatorAuthConduitTokenRevoker.php',
     'PhabricatorAuthConfirmLinkController' => 'applications/auth/controller/PhabricatorAuthConfirmLinkController.php',
@@ -8455,6 +8456,7 @@
     'PhabricatorAuthChallengeStatusController' => 'PhabricatorAuthController',
     'PhabricatorAuthChallengeUpdate' => 'Phobject',
     'PhabricatorAuthChangePasswordAction' => 'PhabricatorSystemAction',
+    'PhabricatorAuthChangeUsernameMessageType' => 'PhabricatorAuthMessageType',
     'PhabricatorAuthConduitAPIMethod' => 'ConduitAPIMethod',
     'PhabricatorAuthConduitTokenRevoker' => 'PhabricatorAuthRevoker',
     'PhabricatorAuthConfirmLinkController' => 'PhabricatorAuthController',
diff --git a/src/applications/auth/message/PhabricatorAuthChangeUsernameMessageType.php b/src/applications/auth/message/PhabricatorAuthChangeUsernameMessageType.php
new file mode 100644
--- /dev/null
+++ b/src/applications/auth/message/PhabricatorAuthChangeUsernameMessageType.php
@@ -0,0 +1,29 @@
+<?php
+
+final class PhabricatorAuthChangeUsernameMessageType
+  extends PhabricatorAuthMessageType {
+
+  const MESSAGEKEY = 'user.edit.username';
+
+  public function getDisplayName() {
+    return pht('Username Change Instructions');
+  }
+
+  public function getShortDescription() {
+    return pht(
+      'Guidance in the "Change Username" dialog for requesting a '.
+      'username change.');
+  }
+
+  public function getFullDescription() {
+    return pht(
+      'When users click the "Change Username" action on their profile pages '.
+      'but do not have the required permissions, they will be presented with '.
+      'a message explaining that they are not authorized to make the edit.'.
+      "\n\n".
+      'You can optionally provide additional instructions here to help users '.
+      'request a username change, if there is someone specific they should '.
+      'contact or a particular workflow they should use.');
+  }
+
+}
diff --git a/src/applications/people/controller/PhabricatorPeopleRenameController.php b/src/applications/people/controller/PhabricatorPeopleRenameController.php
--- a/src/applications/people/controller/PhabricatorPeopleRenameController.php
+++ b/src/applications/people/controller/PhabricatorPeopleRenameController.php
@@ -23,13 +23,22 @@
     $done_uri = $this->getApplicationURI("manage/{$id}/");
 
     if (!$viewer->getIsAdmin()) {
-      return $this->newDialog()
+      $dialog = $this->newDialog()
         ->setTitle(pht('Change Username'))
         ->appendParagraph(
           pht(
             'You can not change usernames because you are not an '.
             'administrator. Only administrators can change usernames.'))
         ->addCancelButton($done_uri, pht('Okay'));
+
+      $message_body = PhabricatorAuthMessage::loadMessageText(
+        $viewer,
+        PhabricatorAuthChangeUsernameMessageType::MESSAGEKEY);
+      if (strlen($message_body)) {
+        $dialog->appendRemarkup($message_body);
+      }
+
+      return $dialog;
     }
 
     $validation_exception = null;