diff --git a/django/contrib/auth/forms.py b/django/contrib/auth/forms.py
index ee09a626a..711dba529 100644
--- a/django/contrib/auth/forms.py
+++ b/django/contrib/auth/forms.py
@@ -11,8 +11,8 @@ class UserCreationForm(forms.ModelForm):
     """
     A form that creates a user, with no privileges, from the given username and password.
     """
-    username = forms.RegexField(label=_("Username"), max_length=30, regex=r'^[\w.@+-]+$',
-        help_text = _("Required. 30 characters or fewer. Letters, digits and @/./+/-/_ only."),
+    username = forms.RegexField(label=_("Username"), max_length=64, regex=r'^[\w.@+-]+$',
+        help_text = _("Required. 64 characters or fewer. Letters, digits and @/./+/-/_ only."),
         error_messages = {'invalid': _("This value may contain only letters, numbers and @/./+/-/_ characters.")})
     password1 = forms.CharField(label=_("Password"), widget=forms.PasswordInput)
     password2 = forms.CharField(label=_("Password confirmation"), widget=forms.PasswordInput,
@@ -45,8 +45,8 @@ class UserCreationForm(forms.ModelForm):
         return user
 
 class UserChangeForm(forms.ModelForm):
-    username = forms.RegexField(label=_("Username"), max_length=30, regex=r'^[\w.@+-]+$',
-        help_text = _("Required. 30 characters or fewer. Letters, digits and @/./+/-/_ only."),
+    username = forms.RegexField(label=_("Username"), max_length=64, regex=r'^[\w.@+-]+$',
+        help_text = _("Required. 64 characters or fewer. Letters, digits and @/./+/-/_ only."),
         error_messages = {'invalid': _("This value may contain only letters, numbers and @/./+/-/_ characters.")})
 
     class Meta:
@@ -63,7 +63,7 @@ class AuthenticationForm(forms.Form):
     Base class for authenticating users. Extend this to get a form that accepts
     username/password logins.
     """
-    username = forms.CharField(label=_("Username"), max_length=30)
+    username = forms.CharField(label=_("Username"), max_length=64)
     password = forms.CharField(label=_("Password"), widget=forms.PasswordInput)
 
     def __init__(self, request=None, *args, **kwargs):
diff --git a/django/contrib/auth/models.py b/django/contrib/auth/models.py
index ed5349453..e3e947700 100644
--- a/django/contrib/auth/models.py
+++ b/django/contrib/auth/models.py
@@ -189,7 +189,7 @@ class User(models.Model):
 
     Username and password are required. Other fields are optional.
     """
-    username = models.CharField(_('username'), max_length=64, unique=True, help_text=_("Required. 30 characters or fewer. Letters, numbers and @/./+/-/_ characters"))
+    username = models.CharField(_('username'), max_length=64, unique=True, help_text=_("Required. 64 characters or fewer. Letters, numbers and @/./+/-/_ characters"))
     first_name = models.CharField(_('first name'), max_length=30, blank=True)
     last_name = models.CharField(_('last name'), max_length=30, blank=True)
     email = models.EmailField(_('e-mail address'), blank=True)