In Norse and Teutonic mythology, the god of battles, whom the Anglo-Saxons called Týw, from where ‘Tuesday’ is derived. He was a member of the Aesir (principal warrior gods).
Tyr sacrificed his right hand as a pledge when the monster Fenriswolf, son of the god-giant Loki, was being bound with an unbreakable magic chain. The wolf, scenting a trap when asked to pitch his strength against the apparently flimsy tethers, refused to take part unless one of the gods placed a hand in his mouth.
At Ragnarök, the final battle between the gods and forces of evil, he was to slay Garm, the hound of the cave leading to the underworld, but would be mortally wounded in the conflict.
It is possible that he was originally a sky-god, his name being cognate with the Greek Zeus, but he was identified by the Romans with Mars; Tuesday corresponds with the Latin Martis dies and the French mardi.