Danger: Diabolik (Italian: Diabolik) is a 1968 action and crime film directed and co-written by Mario Bava, based on the Italian comic series Diabolik by Angela and Luciana Giussani. The film is about a criminal named Diabolik (John Phillip Law), who plans large-scale heists for his girlfriend Eva Kant (Marisa Mell). Diabolik is pursued by Inspector Ginko (Michel Piccoli), who blackmails the gangster Ralph Valmont (Adolfo Celi) into catching Diabolik for him.

An adaptation of the comics was originally envisioned by producer Tonino Cervi, who set up an international co-production deal in 1965 and hired Seth Holt to direct the film with a cast that included Jean Sorel, Elsa Martinelli and Gilbert Roland. Appalled with Holt's footage, distributor Dino De Laurentiis assumed control of the film's production, electing to restart the project from scratch with a new screenplay and Bava as director. De Laurentiis produced the film in tandem with another comic book adaptation, Barbarella, with the two projects receiving financial support from Paramount Pictures and sharing several cast and crew members. Catherine Deneuve was initially cast as Eva, but her incompatibility with Law and disagreements with Bava led to the part being recast with Mell. Working under more financial and creative pressure than he was familiar with, Bava delivered Danger: Diabolik considerably below its assigned budget by utilizing many of the inexpensive visual effects techniques that he had used in his earlier films; it would prove to be the only film that he would direct for a major Hollywood studio.

Upon its theatrical release, Danger: Diabolik performed below De Laurentiis' expectations at the box office, and received negative reviews from The New York Times and Variety. With the re-evaluation of Bava's filmography, retrospective reception of the film has been more positive, with its visuals, the performances of Law and Mell, and the score by Ennio Morricone receiving praise. In studies of the film, critics and historians have focused on Bava's use of mise-en-scène to replicate the imagery and stylization of comic books, and the film's reflection of the socio-political upheavals of the 1960s in its characterization and narratology. Having garnered a cult following, Danger: Diabolik was chosen by Empire magazine as one of "The 500 Greatest Movies of All Time" in 2008. The first in a planned trilogy of new Diabolik films directed by the Manetti Bros. was released in 2021.