Thor (Old Norse: Þórr) is the Norse god of thunder, the sky, and agriculture. He is the son of Odin, chief of the gods, and Odin's consort Jord (Earth) and husband of the fertility goddess Sif, who is the mother of his son Modi and daughter Thrud; his other son, Magni, may be from a union with the giantess Jarnsaxa.
Thor was the defender of Asgard, realm of the gods, and Midgard, the human realm, and is primarily associated with protection through great feats of arms in slaying giants. The majority of the tales featuring Thor, in fact, put him in conflict with a giant or with his nemesis the Midgard Serpent (Jörmungandr, the “huge monster”), a monstrous snake who coils and twists itself around the world. Like almost all of the Norse gods, Thor is doomed to die at Ragnarök, the end of the world and twilight of the gods, but falls only after killing the great serpent with his powerful hammer Mjollnir, dying to its poison; his sons Magni and Modi survive Ragnarök along with a small number of other gods and inherit his hammer which they use to restore order.
He developed from the earlier Germanic god Donar and became the most popular deity of the Norse pantheon. Thor continues as a popular god in the present day, too, and the modern English and German words for the fifth day of the week – Thursday and Donnerstag – both allude to Thor/Donar (“Thor's Day”/“Donar's Day”). He was thought to have ruled the sky from his land of Þrúðvangr (“Power-Field” or “Plains of Strength”) where he built his great hall of Bilskírnir, a palace of 540 rooms.
Thor's popularity reached its height during the Viking Age (c. 790-1100) at which time he was considered the greatest rival to Christ when, roughly from the 10th century onwards, Christianity was introduced to Scandinavia. More amulets and charms of Thor's hammer date from the period when Christianity and the Norse religion were in contention than from any other. Christianity finally prevailed and the cult of Thor was gradually replaced by the new religion by the 12th century.