In Norse mythology, Fenrir or Fenrisulfr is a wolf, the son of Loki and the giantess Angrboša. Fenrir is bound by the gods, but is ultimately destined to grow too large for his bonds and swallow Odin whole during the course of Ragnarök. He will be slain by Odin's son, Višarr, who will use a shoe made throughout time using the pieces of leather waste left over from repaired shoes to hold the lower jaw while he grasped the upper up, tearing the beast apart and avenging his father.

Fenrir has two sons, Hati ('hate') and Skoll.