Thorfinn Sigurdsson, also known as Thorfinn the Mighty, was an 11th-century Jarl of Orkney. He was the youngest of five sons of Jarl Sigurd Hlodvirsson and the only one resulting from Sigurd's marriage to a daughter of Malcolm II of Scotland. He ruled alone as jarl for about a third of the time that he held the title and jointly with one or more of his brothers or with his nephew Rögnvald Brusason for the remainder. Thorfinn married Ingibiorg Finnsdottir, daughter of Finn Arnesson, Jarl of Halland.
The Brough of Deerness - a Viking age ecclesiastical ruin here is associated with Thorkel Fosterer.
A coin from the reign of Olaf Haraldsson of Norway dated 1023–28.
Kalf Arnesson with the young Magnus at the Battle of Stiklestad: 19th century illustration by Halfdan Egedius
One of two surviving pages of an early version of the Heimskringla known as the "Kringla leaf", which is kept in the National and University Library of Iceland. The text is part of Óláfs saga helga.
Earl of Orkney, historically Jarl of Orkney, is a title of nobility encompassing the archipelagoes of Orkney and Shetland, which comprise the Northern Isles of Scotland. Originally founded by Norse invaders, the status of the rulers of the Northern Isles as Norwegian vassals was formalised in 1195. Although the Old Norse term jarl is etymologically related to "earl", and the jarls were succeeded by earls in the late 15th century, a Norwegian jarl is not the same thing. In the Norse context the distinction between jarls and kings did not become significant until the late 11th century and the early jarls would therefore have had considerable independence of action until that time. The position of Jarl of Orkney was eventually the most senior rank in medieval Norway except for the king himself.
Ruins on the Brough of Birsay, once the seat of the early Norse jarls of Orkney. The Brough is now a tidal islet but in earlier times it was connected to Mainland Orkney by an isthmus.
