King Bowser is the main antagonist of Illumination's 13th feature film The Super Mario Bros. Movie, an adaptation of Nintendo's Mario franchise.
He is the tyrannical king of the Koopas and the ruler of the Koopa Kingdom and Darklands who desires to conquer the world using the powerful Super Star. With the assistance of his Koopa Army and loyal servant Kamek, Bowser plans to use the Super Star to target the Mushroom Kingdom and win Princess Peach's hand in marriage, with his plan bringing him into conflict with Mario after kidnapping his brother, Luigi, viewing the former as his rival to winning Peach's love and eventually becomes his arch-nemesis.
He is voiced by Jack Black, while his grunts and roars are done by Kenny James.