Kamen Rider Kiva the Movie: King of the Castle in the Demon World (劇場版 仮面ライダーキバ 魔界城の王, Gekijōban Kamen Raidā Kiba Makaijō no Ō) is the theatrical film adaptation of the Japanese 2008 Kamen Rider series, Kamen Rider Kiva, directed by Ryuta Tasaki and written by Toshiki Inoue. A director's cut came out in June 2009.

The film is produced by Ishimori Productions and Toei, the producers of all the previous television series and films of the Kamen Rider series. Following the tradition of all Heisei Kamen Rider movies, it is a double bill with the movie for 2008's Super Sentai series Engine Sentai Go-onger, Engine Sentai Go-onger: Boom Boom! Bang Bang! GekijōBang!!, both of which premiered on August 9, 2008. The film's title is translated into English as Masked Rider Kiva The Movie: King of the Castle in the Demon World. The double-feature opened at number 4 in Japanese box offices its opening weekend.