Norwegian noble who defeated Harald (Harald I) II Graycloak, becoming the chief ruler (c. 970) of Norway; he later extended his rule over the greater part of the country. He resisted an attempt by the Danish king Harald III Bluetooth to Christianize Norway and was the last non-Christian Norwegian ruler.

The son of the Norwegian earl of Lade, who was killed by Harald II Graycloak (Harald II Eiriksson), Haakon was exiled to Denmark after his father's death. After overthrowing his father's murderer with the aid of Harald Bluetooth, he became sovereign in the west, while Harald Bluetooth annexed southeastern Norway. Haakon supported Bluetooth against the Holy Roman emperor Otto II in 974 but revolted against Bluetooth's efforts to impose Christianity in Norway, subsequently expanding his own sovereignty in the western and northern regions of the country.

Haakon's advocacy of the ancient Norse religion gained him great popularity among the non-Christian Norwegian chieftains. His arrogance toward the end of his life, however, cost him the support of his followers, and he was killed by his own men in 995. He was immediately succeeded by Olaf I Tryggvason, who had invaded Norway earlier that year.