Godzilla vs. Mechagodzilla (ゴジラ対メカゴジラ, Gojira tai Mekagojira) is a 1974 Japanese action-adventure kaiju film directed by Jun Fukuda, with special effects by Teruyoshi Nakano. Distributed by Toho and produced under their effects subsidiary Toho–Eizo, it is the 14th film of the Godzilla franchise, and features the fictional monster characters Godzilla, Anguirus, and King Caesar, along with the mecha character Mechagodzilla. The film stars Masaaki Daimon, Kazuya Aoyama, Gorō Mutsumi, and Akihiko Hirata, with Isao Zushi as Godzilla, Satoru Kuzumi as both Anguirus and King Caesar, and Kazunari Mori as Mechagodzilla. The film marks the first appearances of King Caesar and Mechagodzilla in the franchise.

Godzilla vs. Mechagodzilla was released theatrically in Japan on March 21, 1974, to generally positive reviews. The film received a limited release in the United States in 1977 by Cinema Shares, under the title Godzilla vs. the Bionic Monster. It was then quickly re-released under the title Godzilla vs. the Cosmic Monster which was also the UK theatrical title. The film was followed up with a direct sequel in 1975 titled Terror of Mechagodzilla.