The Magic Serpent (怪竜大決戦 Kairyū Daikessen?, The Mystic Dragons' Decisive Battle) is a 1966 tokusatsu kaiju/ninja fantasyfilm produced by Toei Company Ltd. This film is a loose retelling of the famous Japanese folktale, Jiraiya Gōketsu Monogatari (The Tale of the Gallant Jiraiya).

Just like Toei's many superhero shows, this film is just as action-packed and colorful. And to entertain younger audiences, the heroJiraiya and the villain Orochimaru use ninja magic to transform into daikaiju to battle each other (this was also done in the original story, even though the animals were not necessarily gigantic). Despite the many differences between this film and its source material, this has remained a cult classic.