diff --git a/django/contrib/auth/forms.py b/django/contrib/auth/forms.py
index d6b5702fff..ca7529ab5f 100644
--- a/django/contrib/auth/forms.py
+++ b/django/contrib/auth/forms.py
@@ -61,6 +61,11 @@ class UsernameField(forms.CharField):
     def to_python(self, value):
         return unicodedata.normalize('NFKC', super().to_python(value))
 
+    def widget_attrs(self, widget):
+        attrs = super().widget_attrs(widget)
+        attrs['autocapitalize'] = 'none'
+        return attrs
+
 
 class UserCreationForm(forms.ModelForm):
     """
diff --git a/tests/auth_tests/test_forms.py b/tests/auth_tests/test_forms.py
index 825138755d..e12cf0161f 100644
--- a/tests/auth_tests/test_forms.py
+++ b/tests/auth_tests/test_forms.py
@@ -261,6 +261,10 @@ class UserCreationFormTest(TestDataMixin, TestCase):
             ['The password is too similar to the first name.'],
         )
 
+    def test_username_field_autocapitalize_none(self):
+        form = UserCreationForm()
+        self.assertEqual(form.fields['username'].widget.attrs.get('autocapitalize'), 'none')
+
 
 # To verify that the login form rejects inactive users, use an authentication
 # backend that allows them.
@@ -439,6 +443,10 @@ class AuthenticationFormTest(TestDataMixin, TestCase):
         username_field = User._meta.get_field(User.USERNAME_FIELD)
         self.assertEqual(form.fields['username'].label, capfirst(username_field.verbose_name))
 
+    def test_username_field_autocapitalize_none(self):
+        form = AuthenticationForm()
+        self.assertEqual(form.fields['username'].widget.attrs.get('autocapitalize'), 'none')
+
     def test_username_field_label_empty_string(self):
 
         class CustomAuthenticationForm(AuthenticationForm):
@@ -728,6 +736,10 @@ class UserChangeFormTest(TestDataMixin, TestCase):
         form = UserChangeFormWithoutPassword()
         self.assertNotIn('password', form.fields)
 
+    def test_username_field_autocapitalize_none(self):
+        form = UserChangeForm()
+        self.assertEqual(form.fields['username'].widget.attrs.get('autocapitalize'), 'none')
+
 
 @override_settings(TEMPLATES=AUTH_TEMPLATES)
 class PasswordResetFormTest(TestDataMixin, TestCase):