Joan Lui (also known as Joan Lui - Ma un giorno nel paese arrivo io di lunedì) is a 1985 Italian musical comedy film by Adriano Celentano.

Joan Lui is a singer who has come from another world to condemn the hypocrisy and atrocities of the Western culture.

When he arrives in Italy, he seeks to create a band composed of young and inexperienced musicians to better spread his message.

After having exposed the deception of a major musical producer, Joan Lui disappears into thin air.

The film was the center of a dispute between Mario and Vittorio Cecchi Gori and Celentano as the producers decided, a month after theatrical release, to replace the original cut with another version with a different editing and 30 minutes shorter.