diff --git a/Lib/test/test_urllib2.py b/Lib/test/test_urllib2.py
index fad95cc70e0..f9a76a3f76c 100644
--- a/Lib/test/test_urllib2.py
+++ b/Lib/test/test_urllib2.py
@@ -1252,6 +1252,21 @@ class HandlerTests(unittest.TestCase):
     def test_basic_auth_with_single_quoted_realm(self):
         self.test_basic_auth(quote_char="'")
 
+    def test_basic_auth_with_unquoted_realm(self):
+        opener = OpenerDirector()
+        password_manager = MockPasswordManager()
+        auth_handler = urllib.request.HTTPBasicAuthHandler(password_manager)
+        realm = "ACME Widget Store"
+        http_handler = MockHTTPHandler(
+            401, 'WWW-Authenticate: Basic realm=%s\r\n\r\n' % realm)
+        opener.add_handler(auth_handler)
+        opener.add_handler(http_handler)
+        self._test_basic_auth(opener, auth_handler, "Authorization",
+                              realm, http_handler, password_manager,
+                              "http://acme.example.com/protected",
+                              "http://acme.example.com/protected",
+                              )
+
     def test_proxy_basic_auth(self):
         opener = OpenerDirector()
         ph = urllib.request.ProxyHandler(dict(http="proxy.example.com:3128"))
diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
index a5f0866cb6b..6cc78edc428 100644
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -895,7 +895,7 @@ class AbstractBasicAuthHandler:
     # allow for double- and single-quoted realm values
     # (single quotes are a violation of the RFC, but appear in the wild)
     rx = re.compile('(?:.*,)*[ \t]*([^ \t]+)[ \t]+'
-                    'realm=(["\'])(.*?)\\2', re.I)
+                    'realm=(["\']?)([^"\']*)\\2', re.I)
 
     # XXX could pre-emptively send auth info already accepted (RFC 2617,
     # end of section 2, and section 1.2 immediately after "credentials"
diff --git a/Misc/NEWS b/Misc/NEWS
index 95a2c4f2f1e..009d8e69236 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -31,6 +31,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #12541: Be lenient with quotes around Realm field of HTTP Basic
+  Authentation in urllib2.
+
 - Issue 14807: move undocumented tarfile.filemode() to stat.filemode() and add
   doc entry. Add tarfile.filemode alias with deprecation warning.