Thor (Old Norse Þórr, Anglo-Saxon Þunor, whence Thursday) was the god of thunder, of storms, of the strength of arm that stood between the gods and their giant enemies. He was the son of Odin and the earth-goddess Jörð (or, in some versions, Fjörgynn), red-bearded and immensely strong, the most popular of the Norse gods to judge by the great number of personal names compounded with his (Thorvald, Thorgrim, Thorkel, Thorbjörn, and so on, by the thousands in Icelandic and Scandinavian tradition). His weapon was the great hammer Mjölnir, forged for him by the dwarves; thrown, it never missed its target and always returned to his hand; small enough to be hidden in his clothing when he traveled. He wore the iron gauntlets Járngreipr to grip the hammer, and the belt Megingjörð that doubled his already prodigious strength. He drove a chariot drawn by two goats, Tanngrisnir and Tanngnjóstr, which he could slaughter and eat at need, then wrap their bones in their hides and resurrect them by raising the hammer over them.

Thor's principal enemies were the giants (jötnar), against whom he undertook countless expeditions; the Eddas record more of his individual narratives than of any other Norse god. He fished for the World-Serpent Jörmungandr from a boat with the giant Hymir, hauling the monster up by a hook baited with an ox's head; he would have killed the serpent then, but Hymir in terror cut the line. He was outwitted (the only such case) by the giant-king Útgarða-Loki on a journey into Jötunheim, where he discovered that an old woman who had defeated him at wrestling was Old Age, that a great drinking-horn he could not empty was the ocean, that a cat he could not lift was the World-Serpent in disguise — that the giants had used illusion against him, but that the apparent failure had been, by other measures, a series of cosmic-scale victories. He killed the giant Geirrod, the giantess Hrungnir, the giant Thrym (who had stolen the hammer Mjölnir, and forced Thor to retrieve it disguised as a bride at the wedding-feast — a comic narrative of considerable charm in the Þrymskviða). At Ragnarök, Thor would kill Jörmungandr with the hammer but would die nine paces later from the serpent's venom; the prophecy was old and was understood as fixed.