Hatchet for the Honeymoon (Italian: Il rosso segno della follia, lit. 'The Red Sign of Madness') is a 1970 giallo film directed by Mario Bava and starring Stephen Forsyth, Dagmar Lassander, Laura Betti, and Femi Benussi. The story follows John Harrington, a hatchet-wielding madman who murders young brides in an effort to recall a childhood trauma.

The film's production was troubled, with tensions among the cast and crew, location difficulties, a major subplot concerning Harrington's relationship with his wife being added solely to accommodate Betti's casting, and a significant hiatus in filming when the budget ran out. It was not released until a year after it was completed, and was largely ignored by both critics and audiences, remaining one of Bava's most obscure films even after his work achieved cult popularity.