Olaf Haraldsson (d. 934) was son of Harald Fairhair of Norway. He was made king of Vingulmark by his father and then later inherited Vestfold after his brother Bjørn Farmann had been killed by their half-brother Eirik Bloodaxe. Eirik was king Harald's favourite son and his appointed successor, but he was not very popular among his half-brothers. Upon his father's death, Olaf made himself king of eastern Norway, and allied himself with another half-brother, Sigrød , against Eirik. The three kings met in battle outside Tønsberg. Olaf and Sigrød were defeated and they both fell there. Olaf's son, Tryggve Olavsson, later became king of Ranrike and Vingulmark.