In Nordic mythology, Fenrir ("swamp dweller") or Fenrisúlfr ("Fenrir wolf"). Fenris is a gigantic wolf, son of the god Loki and the giant Angrboda, messenger of misfortune. He has for brother Jörmungandr, the serpent of Midgard, and for sister Hel, who reigns over the world of the dead. Considered too powerful and dangerous by the gods, Fenrir is cunningly chained and released for the prophetic battle Ragnarök during which he will swallow Odin and then be violently shot by Vidar, one of the god's sons.

In northern eschatology, it is prophesized that a great battle will take place in which the giants, led by the god Loki, will attack the Ases on the plain of Vígríd. This event is called Ragnarök. All the chains will break, and the Fenrir wolf, like his father Loki, will be released. The fire giant Surt will fight alongside the other forces of chaos and ignite the world, which will sink in the ocean. During this battle, the majority of the gods, and all men except a couple, Líf and Lífþrrasir, will perish. Several texts agree that the god Odin will be killed by the monstrous wolf Fenrir. Then Odin's son, Vidar, will avenge his father, killing Fenrir by snatching his jaw or piercing his heart with his sword.