diff --git a/django/apps/config.py b/django/apps/config.py
index 6d794eee3a..bced53d506 100644
--- a/django/apps/config.py
+++ b/django/apps/config.py
@@ -34,6 +34,10 @@ class AppConfig:
         # This value must be unique across a Django project.
         if not hasattr(self, 'label'):
             self.label = app_name.rpartition(".")[2]
+        if not self.label.isidentifier():
+            raise ImproperlyConfigured(
+                "The app label '%s' is not a valid Python identifier." % self.label
+            )
 
         # Human-readable name for the application e.g. "Admin".
         if not hasattr(self, 'verbose_name'):
diff --git a/tests/apps/tests.py b/tests/apps/tests.py
index 0e1f918bcc..a8a93ce683 100644
--- a/tests/apps/tests.py
+++ b/tests/apps/tests.py
@@ -436,6 +436,14 @@ class AppConfigTests(SimpleTestCase):
         ac = AppConfig('label', Stub(__path__=['a']))
         self.assertEqual(repr(ac), '<AppConfig: label>')
 
+    def test_invalid_label(self):
+        class MyAppConfig(AppConfig):
+            label = 'invalid.label'
+
+        msg = "The app label 'invalid.label' is not a valid Python identifier."
+        with self.assertRaisesMessage(ImproperlyConfigured, msg):
+            MyAppConfig('test_app', Stub())
+
     @override_settings(
         INSTALLED_APPS=['apps.apps.ModelPKAppsConfig'],
         DEFAULT_AUTO_FIELD='django.db.models.SmallAutoField',