Týr sacrificed his right hand while the gods bound the wolf Fenrir.
Fenrir was the monstrous wolf born to Loki and the jötunn Angrboða. The gods feared him because prophecies foretold that he would become a great danger, so they tried to restrain him with magical fetters. The final binding, Gleipnir, looked like a thin ribbon but was made from six impossible ingredients, including mountain roots and the sound of a cat’s footfall.
Fenrir suspected deception and demanded that one of the gods place a hand in his mouth as a pledge that he would be released. Týr, renowned for courage and associated with law and war, volunteered. Once Gleipnir held firm, the gods refused to free Fenrir, and the wolf bit off Týr’s hand at the wrist. This is why Týr is often described as one-handed.
The story is sometimes misremembered as Odin losing a hand or as Týr willingly cutting it off. In the surviving myth, Fenrir bites it off. At Ragnarök, Fenrir escapes and kills Odin, while Týr is foretold to fight the hound Garmr.