The Norse god who lost his hand to the wolf Fenrir was Týr.
Týr sacrificed his right hand while the gods bound Fenrir, the monstrous wolf and son of Loki. The gods used the magical fetter Gleipnir, which looked like a thin ribbon but was stronger than any ordinary chain. Fenrir distrusted the gods and agreed to be bound only if one of them placed a hand in his mouth as a pledge that he would be released.
Týr alone had the courage to make that bargain. Once Fenrir realized that Gleipnir would not be removed, he bit down and tore off Týr’s hand at the wrist, a place later called the “wolf-joint.” The episode is presented as evidence of Týr’s bravery and willingness to keep faith, even when the gods were deceiving Fenrir.
Týr is often described as a god of war, courage, law, or justice, though surviving Norse sources give him a less complete profile than Odin or Thor. Do not confuse him with Víðarr: at Ragnarök, Víðarr—not Týr—kills Fenrir in revenge for the wolf’s destruction of Odin.