Yokai Monsters: Spook Warfare (Japanese: 妖怪大戦争, Hepburn: Yōkai Daisensō, lit. 'The Great Yokai War') is a 1968 Japanese fantasy horror film directed by Yoshiyuki Kuroda. It is the second in a trilogy of films produced in the late 1960s, all of which focus around traditional Japanese monsters known as yōkai. (It was preceded by Yokai Monsters: 100 Monsters (1968), and was followed by Yokai Monsters: Along with Ghosts (1969).)

Yokai Monsters: Spook Warfare, along with the other two films in the series, was produced by Daiei Film and makes extensive use of tokusatsu special effects, with the majority of the creatures being represented by actors in costumes or puppets. The film was made in Fujicolor and Daieiscope.

In 2005, director Takashi Miike released The Great Yokai War, a modern retelling of the story which borrows many elements from Spook Warfare.