In Norse mythology, Fenrir is the wolf that swallows Odin at Ragnarök. Fenrir is the monstrous son of Loki and the giantess Angrboða, and he is destined to break free and attack the gods.
The gods become fearful of Fenrir’s growing strength and bind him with the magical fetter Gleipnir. Although Gleipnir looks delicate, it is made from impossible ingredients such as the sound of a cat’s footfall and the beard of a woman. Fenrir is suspicious and agrees to the binding only when Týr places a hand in his mouth as a pledge.
Fenrir eventually breaks free during Ragnarök and kills Odin. Odin’s son Víðarr then avenges him by killing Fenrir. The episode is distinct from the story of Sköll and Hati, wolves associated with the sun and moon.
Some modern accounts call Fenrir “Fenrisúlfr,” meaning Fenrir’s wolf. These names refer to the same mythological creature.