diff --git a/django/conf/__init__.py b/django/conf/__init__.py
index 97f26e9aa3..c887890a0c 100644
--- a/django/conf/__init__.py
+++ b/django/conf/__init__.py
@@ -106,6 +106,9 @@ class Settings(BaseSettings):
                     setting_value = (setting_value,) # In case the user forgot the comma.
                 setattr(self, setting, setting_value)
 
+        if not self.SECRET_KEY:
+            raise ValueError("The SECRET_KEY setting mustn't be empty.")
+
         if hasattr(time, 'tzset') and self.TIME_ZONE:
             # When we can, attempt to validate the timezone. If we can't find
             # this file, no check happens and it's harmless.