Thorfinn Turf-Einarsson, Earl of Orkney

Thorfinn Torf-Einarsson also known as Thorfinn Skull-splitter (from the Old Norse Þorfinnr hausakljúfr) was a 10th-century Earl of Orkney. He appears in the Orkneyinga saga and briefly in St Olaf's Saga, as incorporated into the Heimskringla. These compelling stories were first written down in Iceland in the early 13th century and much of the information they contain is "hard to corroborate".

Thorfinn was the youngest son of Torf-Einarr, himself the son of Rognvald Eysteinsson, the first Earl of Orkney. Torf-Einarr had two other sons, Arnkel and Erlend who "fell in a war expedition" at an unspecified location in England along with Erik Bloodaxe. Erik's widow, Gunnhildr then fled north to Orkney with her sons who used the islands as a base for summer raiding expeditions.

Thorfinn had five sons: Arnfinn, Havard, Hlodvir, Ljot, and Skuli. Their mother was Grelad, a daughter of "Earl Dungad of Caithness" and Groa, herself a daughter of Thorstein the Red. Grelad's Norse credentials were thus impressive, but it has been suggested that her connection to this "earl" of Caithness may have been more important for the Orkney earldom. It is likely that Dungad was a member of a pre-Norse era ruling family and that the marriage brought Groa's descendents within the Celtic derbfine and helped to legitimise their ambitions on the north mainland of Scotland. Thorfinn and Grelod also had two daughters whose names are not known, each of whom had a son called Einar - Einar kliningr ("Buttered-bread") and Einar harðkjotr ("Hard-mouth").

Gunnhildr and her family later set out for Norway, but before they left they "gave" their daughter Ragnhild Eriksdotter to Arnfinn Thorfinnsson in marriage. In the later days of Thorfinn's rule, the sons of Eric Bloodaxe fled Norway and returned to Orkney where they "committed great excesses".