Peter St John, 9th Earl of Orkney

Earldom of Orkney (creation of 1696)
Arms of the 8th Earl of Orkney: Quarterly: 1st and 4th grandquarters, Argent on a Saltire Gules a Lymphad sails furled Or a Chief Ermine (Fitz-Maurice); 2nd grandquarter, quarterly: 1st and 4th, Gules three Cinquefoils Ermine (Hamilton); 2nd, Argent a Lymphad sails furled Sable (Arran); 3rd, Argent a Heart Gules imperially crowned Or on a Chief Azure three Mullets of the first (Douglas); over all at the fess point an Escallop Or for difference (for Lord George Hamilton, 1st Earl of Orkney); 3rd grandquarter, quarterly: 1st and 4th, Gules three Lions passant guardant per pale Or and Argent (O'Brien); 2nd, Argent three Piles meeting in the point issuing from the chief Gules; 3rd, Argent a Pheon Azure.
Creation date	3 January 1696 (third creation)
Monarch	William II of Scotland
Peerage	Peerage of Scotland
First holder	Lord George Hamilton
Present holder	Oliver St John, 9th Earl of Orkney
Heir apparent	Oliver Robert St John, Viscount Kirkwall
Remainder to	heirs whatsoever of the 1st Earl (a woman can succeed if she has no brothers or if all her brothers died childless)
Subsidiary titles	Viscount of Kirkwall Lord Dechmont
Former seat(s)	Kirkwall Castle

The Earl of Orkney was originally a Norse jarl ruling Norðreyjar (Orkney, Shetland, Caithness and Sutherland). Originally founded by Norse invaders, the status of Norðreyjar as a Norwegian vassal was formalised in 1195. Although the term Jarl looks similar to Earl, and the Jarls were succeeded by Earls in the late 15th century, a Norwegian Jarl is not the same thing; in fact, the position of Jarl of Orkney was the most senior rank in mediaeval Norway except for the king himself.

The Jarls were periodically subject to the kings of Alba for those parts of their territory in what is now mainland Scotland (i.e. Caithness and Sutherland). In 1232, a Scottish dynasty descended from the Mormaers of Angus replaced the previous family descended from the Mormaers of Atholl, although it remained formally subject to Norway. This family was in turn replaced by the descendants of the Mormaers of Strathearn and later still by the Sinclair family, during whose time Orkney passed to Scots control.

Rognvald Eysteinsson, Earl of Møre fl. 865–890 is sometimes credited with being the founder of the jarldom. By implication the Orkneyinga saga identifies him as such for he is given "dominion" over Orkney and Shetland by King Harald Finehair, although there is no concrete suggestion he ever held the title. The Heimskringla states that his brother Sigurd was the first to formally hold the title.

Sigurd's son Guthorm ruled for a year and died childless. Rognvald's son Hallad then inherited the title. However, unable to constrain Danish raids on Orkney, he gave up the earldom and returned to Norway, which "everyone thought was a huge joke."Torf-Einarr then succeeded in defeating the Danes and founded a dynasty which retained control of the islands for centuries after his death. Smyth (1984) concludes that the role of the brothers Eysteinsson lacks historical credibility and that Torf-Einarr “may be regarded as the first historical earl of Orkney”. Drawing on Adam of Bremen's assertion that Orkney was not conquered until the time of Harald Hardrada, who ruled Norway from 1043–66, Woolf (2007) speculates that Sigurd “the Stout” Hlodvirsson, Torf-Einarr’s great-grandson, may have been the first Earl of Orkney. Dates are largely conjectural, at least until his death recorded in 1014.