Curse of the Crimson Altar is a 1968 British horror film directed by Vernon Sewell and starring Christopher Lee, Boris Karloff, Barbara Steele and Mark Eden. The film was produced by Louis M. Heyward for Tigon British Film Productions. The film was edited and released as The Crimson Cult in the United States. The screenplay, by Doctor Who writers Mervyn Haisman and Henry Lincoln, was based (uncredited) on the short story “The Dreams in the Witch House” by H. P. Lovecraft. This film also featured one of the final film appearances of horror heavyweight Karloff.