Udûn, Iron Mountains, also called Utumno, the underground fortress of Morgoth in the Age of the Lamps, before the First Age of Middle-earth in the writings of J. R. R. Tolkien
Udûn, Mordor, the plain by the Black Gate at the northwestern point of Mordor in the Third Age in the writings of J. R. R. Tolkien
, an episode of the television series, named after the plain in Mordor
