diff --git a/Lib/imaplib.py b/Lib/imaplib.py
index 2c3925958d011b..3ca8328e0af1b2 100644
--- a/Lib/imaplib.py
+++ b/Lib/imaplib.py
@@ -708,7 +708,7 @@ def login(self, user, password):
         """
         typ, dat = self._simple_command('LOGIN', user, self._quote(password))
         if typ != 'OK':
-            raise self.error(dat[-1])
+            raise self.error(dat[-1].decode('UTF-8', 'replace'))
         self.state = 'AUTH'
         return typ, dat
 
diff --git a/Lib/test/test_imaplib.py b/Lib/test/test_imaplib.py
index a13ee58d650e1b..cec3e68b75cae7 100644
--- a/Lib/test/test_imaplib.py
+++ b/Lib/test/test_imaplib.py
@@ -415,6 +415,16 @@ def cmd_AUTHENTICATE(self, tag, args):
                 r'\[AUTHENTICATIONFAILED\] invalid'):
             client.authenticate('MYAUTH', lambda x: b'fake')
 
+    def test_invalid_login(self):
+        class MyServer(SimpleIMAPHandler):
+            def cmd_LOGIN(self, tag, args):
+                self.server.logged = args[0]
+                self._send_tagged(tag, 'NO', '[LOGIN] failed')
+        client, _ = self._setup(MyServer)
+        with self.assertRaisesRegex(imaplib.IMAP4.error,
+                r'\[LOGIN\] failed'):
+            client.login('user', 'wrongpass')
+
     def test_valid_authentication_bytes(self):
         class MyServer(SimpleIMAPHandler):
             def cmd_AUTHENTICATE(self, tag, args):
diff --git a/Misc/NEWS.d/next/Library/2023-02-26-14-07-18.gh-issue-91099._QPbEL.rst b/Misc/NEWS.d/next/Library/2023-02-26-14-07-18.gh-issue-91099._QPbEL.rst
new file mode 100644
index 00000000000000..d886e8ac6032a4
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-02-26-14-07-18.gh-issue-91099._QPbEL.rst
@@ -0,0 +1,2 @@
+:meth:`imaplib.IMAP4.login` now raises exceptions with :class:`str` instead of
+:class:`bytes`. Patch by Florian Best.