Torstein was a Norwegian Viking during the 8th century AD. He served in Ragnarr Lodbrok's warband during his raiding expeditions against the British Isles, including the Sack of Lindisfarne and the Sack of Hexham in 793. After Ragnarr was in hiding after nearly being killed by Earl Haraldson, Torstein was sent by Ragnarr's brother Rollo Sigurdsson to seek him out and ensure that he stayed informed. Torstein told Ragnarr that the Earl had confiscated Ragnarr's boat and intended to use it as the dowry for Thyri Jarlsdottir's wedding to Earl Bjarni.