Tyr (also spelled Tiw), in Norse mythology, a god of war and of courage. A son of the chief god Odin, Tyr lost his right hand when it was bitten off at the wrist by the monstrous wolf Fenrir. According to the 'Prose (or Younger) Edda', Tyr was the bravest and most valiant of the gods, and he had great power over victory in battles.
Although little is known of his cult today, Tyr is believed to be the oldest of the Northwest European gods. His importance to the early Germanic peoples is not disputed, but it is difficult to determine his precise function and significance. His name has been associated with the Roman gods Jupiter and Mars, and with assemblies in which warriors settle disputes. The English word Tuesday comes from the name Tyr, and the German word for Tuesday, Dienstag, is linked to the god, as is the old Norse word thing, meaning an assembly of warriors. It is also known that Tyr had something to do with runic magic and the sacredness of oaths. As Odin's importance began to increase in the Norse pantheon, starting in the 1st century AD, Tyr's probable position as principal god was eclipsed. His function as a battle god also diminished with the increased popularity of Thor. By the time of the 'Prose Edda', Tyr was known as a god to whom "men of action" should pray, and he was associated primarily with the myth of the leashing of the wolf Fenrir.
According to that legend, when Fenrir was still a cub, Tyr undertook the dangerous task of feeding it. It grew so large so quickly that the gods realized that it could destroy them. They attempted to chain it up on the pretext of testing its strength, but twice the wolf broke the fetters. Finally the gods commissioned the dwarfs to forge a stronger chain, and they produced a magic cord, Gleipnir. Fenrir was rightly suspicious of this cord--which, unlike the other fetters, was slender as a ribbon--but rather than have his courage questioned, he said that he would let them put it on him if someone would at the same time put their hand in his mouth as a pledge of good faith. None of the gods, of course, wanted to do this. Then Tyr came forward and silently put his right hand in the wolf's mouth. Only then did the wolf allow himself to be bound. Fenrir kicked and strained at the bond and realized he could not break it, and the gods would not let him loose. He realized he had been tricked, and he closed his mouth on Tyr's hand, biting it off. This sacrificial mutilation, done for the good of the world, demonstrates Tyr's connection with the keeping of oaths.
At Ragnarok, the battle between gods and demons that was to take place at the end of the world, Tyr was fated to slay--and at the same time be slain by--Garm, the hound of Hel, the goddess of the underworld.