Little is known of the first Tancred of Hauteville; his historical importance comes entirely from the accomplishments of his sons and later descendants. He was a minor noble in the Cotentin in Normandy, but it is not even certain which of the 3 villages called Hauteville he held. Various legends later arose about him which have no supporting contemporary evidence.
He had 12 sons by his two wives, and several daughters, almost all of whom left Normandy for southern Italy and acquired some prominence there.
By his first wife Muriel he had 5 sons:
Tancred was a grandson of Robert Guiscard and nephew of Bohemund of Taranto. In 1096 he joined his uncle on the First Crusade, and the two made their way to Constantinople. There, he was pressured to swear an oath to Byzantine emperor Alexius I, promising to give back any conquered land to the Empire. Although the other leaders did not intend to keep their oaths, Tancred refused to swear the oath altogether.
He led the siege of Nicaea in 1097, but the city was taken by Alexius' army after secret negotiations with the Seljuk Turks. Because of this Tancred was very distrustful of the Byzantines. Later in 1097 he captured Tarsus and other cities in Cilicia and helped capture Antioch in 1098.
In 1099 he led the assault on Jerusalem and was the first Crusader to enter the city on July 15. He took hundreds of Muslim prisoners, leading them to safety on the roof of a mosque, but despite his protection they were slaughtered along with the rest of the Muslim population. When the Kingdom of Jerusalem had been established, Tancred became lord of Tiberias.
In 1100 Tancred became regent of Antioch when Bohemund was taken prisoner by the Seljuks. He expanded the territory of the Principality by capturing land from the Byzantines, although over the next decade Alexius attempted, unsucessfully to bring him under Byzantine control. In 1104 he also took control of the County of Edessa when Baldwin I was taken captive. After Baldwin's release in 1107 he had to fight Tancred to regain control of the county; Tancred was eventually defeated and returned to Antioch. In 1110 he brought Krak des Chevaliers under his control, which would later become an important castle in the County of Tripoli. Tancred remained regent in Antioch until his death in 1112.