Nightmare Castle (Italian: Amanti d’Oltretomba) is a 1965 Italian horror film directed by Mario Caiano. The film stars Paul Muller, Helga Liné and Barbara Steele in a dual role.

Mario Caiano shot the film in Rome and declared it his tribute to the Gothic genre and to actress Barbara Steele. Among reviews of the film, critics and historians note Steele's dual performance.