Oistin mac Amlaíb

Oistin mac Amlaíb (Old Norse: Eysteinn Óláfsson) was a ninth-century Norse or Norse-Gael leader who is sometimes identified as a King of Dublin. He was a son of Amlaíb Conung and nephew of Ímar, founder of the Uí Ímair dynasty. He is sometimes identified with Thorstein the Red, a figure who features in the Norse sagas.

The earliest mention of Oistin may be by Cogad Gáedel re Gallaib, which in 873 describes how Bárid mac Ímair and an unnamed son of Amlaíb Conung plundered the caves of Ciarraige. This unnamed son of Amlaíb is probably Oistin. Downham suggests this raid was undertaken as a show of strength; it occurred shortly after the death of Ímar, with Bárid probably succeeding him as King of Dublin. Though Oistin is not named as a king in the annals, it has been suggested by others that Oistin and Bárid ruled together as co-kings after the death of Ímar.

The one and only mention of Oistin by name in contemporary annals is by the Annals of Ulster in 875:

"Albann" is generally agreed to be identical to Halfdan Ragnarsson, supposed son of the legendary Viking Ragnar Lodbrok. Some scholars identify Halfdan as a brother of Amlaíb, Ímar and Auisle, and hence uncle of Oistin. This identification is contingent upon Ímar being identical to Ivar the Boneless: Halfdan and Ivar are named as brothers in the Anglo-Saxon Chronicle. If Halfdan and Oistin were indeed kin, then it may explain the reason for the conflict: it was a dynastic squabble for control of the kingdom.

Some have suggested Oistin is the same person as Thorstein the Red, a figure who features in the Norse sagas. However, this is problematic since Thorstein is said to have died in Scotland after conquering much of the country, whereas Oistin is said to have been killed in Ireland in 875 by Albann (i.e. Halfdan). Similarly, Oistin's father Amlaíb is sometimes identified with Olaf the White, a Viking sea-king who also features in the sagas and is named as the father of Thorstein the Red. The sagas are of dubious historical value, but the figures featured within may be based on real people. To get around the problem whereby Oistin and Thorstein die in different places in different circumstances, but keeping the identification of Amlaíb with Olaf the White, it has been proposed that Oistin and Thorstein were brothers.

Amlaíb Conung is identified as Oistin's father by the Annals of Ulster. A brother, Carlus, is mentioned by the Annals of the Four Masters.

A number of other familial connections are known if the identification of Oistin with Thorstein the red is correct. According to the sagas, Aud the Deep-Minded, daughter of Ketil Flatnose, the King of Isles, was the mother of Thorstein. Thorstein's wife is given as Thurid (Þuríður in Old Norse), the daughter of a Geatish man named Eyvind the Easterner. Their children include at least six daughters, Osk, Vigdis, Olof, Thorhild and Thorgerd, and at least one son, Olaf Feilan.