Here, his origin. Should be good enough to start off with.
Ages ago, Odin, lord of the gods of Asgard, desired a child of both Asgard and Midgard (Earth), and therefore sought out and wooed Gaea, the eldest goddess of the Earth. Gaea gave birth to Thor in a small cave in Norway, and Odin took him to be raised in Asgard by his wife, Frigga.
The young Thor grew up alongside his step-brother Loki, who was always jealous of Thor, the favored son. Thor excelled in power and popularity, and on his eighth birthday, Odin had the hammer Mjolnir created, enchanting it with powerful magic. He decreed that Mjolnir would be presented to Thor when he had been proven a worthy warrior, and Thor spent the next several years training and performing heroic deeds. Indeed, eight years later, Odin gave the hammer to Thor, declaring him to be the greatest warrior in Asgard.
Thor traveled to Earth for the first time in the Ninth Century A.D., in response to his worship among the Vikings. Thor reveled in his worship, leading many in battle and extolling the way of the warrior. Years later, a set of Vikings killed innocent inhabitants of a Christian monastery in Thor’s name. In shock and disillusion, Thor cut himself off from his worshippers and returned to Asgard. The Asgardian religion would never be as fervent, eventually dying out completely over the centuries.
In the other eight worlds of Asgard, however, Thor continued to perform many acts of battle and adventure. Unfortunately, he grew headstrong, proud, and selfish. It pained the heart of Odin. One day, Thor chased a monster into the land of the Frost Giants, a breech of protocol that nearly sparked a war in all of Asgard. Odin had to teach Thor a lesson. He created a mortal body for him, one with a lame leg, and sent Thor, stripped of his powers and memories, to Earth.
