In J. R. R. Tolkien's Middle-earth legendarium, werewolves were servants of Morgoth, wolf-like beasts "inhabited by dreadful spirits" that Sauron had imprisoned in the bodies. Tolkien does not always distinguish between wolf and werewolf, in one place using both terms for the same creature.
Sauron commanded armies of werewolves in the First Age, and on occasion took the shape of a werewolf himself. The first werewolf was Draugluin (whose name contains the root draug, "wolf"). The greatest was Carcharoth, the guardian of Angband, a descendant of Draugluin as all werewolves were.
Werewolves appear in the role-playing video games Middle-earth Role Playing and The Lord of the Rings Roleplaying Game and were set to appear in the role-playing video game The Lord of the Rings: The White Council before it was cancelled.