Harald I (born c. 860—died c. 940) was the first king to claim sovereignty over all of Norway. One of the greatest of the 9th-century Scandinavian warrior chiefs, he gained effective control of Norway’s western coastal districts but probably had only nominal authority in the other parts of Norway.
The son of Halvdan the Black, ruler of part of southeastern Norway and a scion of the Yngling dynasty, the ancient royal house of Sweden, Harald succeeded his father at the age of 10. His first conquest came with the suppression of a revolt in the Uplands region. A pact with Haakon, earl of Lade, enabled him to pursue conquest of the western districts, culminating in the battle of Hafrsfjord, dated 872 by medieval historians but placed 10 to 20 years later by modern historians.
Harald’s conquests and taxation system led many chiefs and their followers to emigrate to the British Isles, adjacent lands, and perhaps to Iceland, which first became known to Scandinavians during the era of Harald’s rule. He acquired wealth through his control of coastal trade but ruled indirectly through lesser chieftains in areas other than his own tightly controlled home district, in the southwest. His major governmental contribution lay in the development of provincial administrations through such chieftains.
The most reliable information on Harald’s life is contained in contemporary poems written down in Iceland in the 13th century. His career is also described in 12th- and 13th-century Icelandic and Norwegian historical works of questionable reliability, the fullest account being written by the Icelander Snorri Sturluson (died 1241) in the Heimskringla.