Harald Fairhair (Old Norse: Haraldr inn hárfagri, Norwegian: Harald hårfagre; putatively c. 850 – c. 932) is portrayed by medieval Icelandic historians as the first King of Norway. According to traditions current in Norway and Iceland in the twelfth and thirteenth centuries, he reigned from c. 872 to 930. Supposedly, two of his sons, Eric Bloodaxe and Haakon the Good, succeeded Harald to become kings after his death.

Most of Harald's biography remains uncertain, since the extant accounts of his life in the sagas were set down in writing around three centuries after his lifetime. Indeed, although it is possible to write a detailed account of Harald as a character in medieval Icelandic sagas (and this entry does), it is even possible to argue that there was no such historical figure at all.

His life is described in several of the Kings' sagas, none of them older than the twelfth century. Their accounts of Harald and his life differ on many points, but it is clear that in the twelfth and thirteenth centuries Harald was regarded as having unified Norway into one kingdom.