Unknown World (a.k.a. Night Without Stars) is a 1951 independently made American black-and-white science fiction adventure film, directed by Terrell O. Morse, and starring Bruce Kellogg, Marilyn Nash, Jim Bannon, and Otto Waldis. Distributed by Lippert Pictures, it was produced by Irving A. Block and Jack Rabin. The film concerns a scientific expedition seeking livable space deep beneath the Earth's surface in the event a nuclear war makes living above ground impossible.