Robot Monster (or Monster from Mars) is a 1953 independently made American black-and-white 3D science fiction horror film, remembered in later decades as one of the worst movies ever made. It was produced and directed by Phil Tucker, written by Wyott Ordung, and stars George Nader, Claudia Barrett, and George Barrows. The production company was Three Dimensional Pictures, Inc. The film was distributed by Astor Pictures.

Robot Monster tells the story of the alien robot Ro-Man's mission to Earth to destroy humanity. He manages to kill all but eight survivors, who have become immune to his death ray. Ro-Man runs afoul of the Great Guidance, his leader, when he becomes attracted to the human Alice. She is the eldest daughter of a surviving scientist, and he refuses to harm her. The Great Guidance must now come to Earth and finish what the Moon robot started.