Guðrøðr Óláfsson, King of the Isles
Guðrøðr Óláfsson (died 10 November 1187) was a twelfth-century ruler of the kingdoms of Dublin and the Isles. Guðrøðr was a son of Óláfr Guðrøðarson, King of the Isles and Affraic, daughter of Fergus, Lord of Galloway. Throughout his career, Guðrøðr battled rival claimants to the throne, permanently losing about half of his realm to a rival dynasty in the process. Although dethroned for nearly a decade, Guðrøðr clawed his way back to regain control of a partitioned kingdom, and proceeded to project power into Ireland. Although originally opposed to the English invasion of Ireland, Guðrøðr adeptly recognised the English ascendancy in the Irish Sea region and aligned himself with the English. All later kings of the Crovan dynasty descended from Guðrøðr.

In the last year of his father's reign, Guðrøðr was absent at the court of Ingi Haraldsson, King of Norway, forging closer ties with the Kingdom of Norway. When Óláfr was assassinated by rival members of the Crovan dynasty in 1153, Guðrøðr returned to the Isles, overthrew his usurping cousins, and seized the throne for himself. Guðrøðr evidently pursued a more aggressive policy than his father, and the following year appears to have lent military assistance to Muirchertach Mac Lochlainn, King of Cenél nEógain in the latter's bid for the high-kingship of Ireland. Not long afterwards, Guðrøðr faced a dynastic challenge from his brother-in-law, Somairle mac Gilla Brigte, Lord of Argyll, whose son, as a grandson of Óláfr, possessed a claim to the throne. Late in 1156, Guðrøðr and Somaile fought an inconclusive sea-battle and partitioned the kingdom of the Isles between them. Two years later Somairle stuck again and forced Guðrøðr from the Isles altogether.

Guðrøðr appears to have spent his exile in the kingdoms of England and Scotland before journeying to Norway. In about 1161, Guðrøðr distinguished himself in the ongoing Norwegian civil wars at the final downfall of Ingi. Guðrøðr made his return to the Isles in 1164, in the aftermath of Somairle's defeat and death at the hands of the Scots. Although he regained the kingship itself, the territories ceded to Somairle in 1156 were retained by the latter's descendants. At some point in his career, Guðrøðr briefly held the kingship of Dublin. Although he was initially successful in fending off Muirchertach, the Dubliners eventually settled with the latter, and Guðrøðr returned to the Isles. This episode may have bearing on Guðrøðr's marriage to Findguala ingen Néill, Muirchertach's granddaughter. In 1170, Dublin fell to an Anglo-Irish alliance. The following year the ousted King of Dublin attempted to retake the town, and Ruaidrí Ua Conchobair, King of Connacht attempted to dislodge the English from Dublin. In both cases, Guðrøðr appears to have provided military assistance against the English. In succeeding years, however, Guðrøðr aligned himself with one of the most powerful English conquerors, John de Courcy. Guðrøðr's assistance to John, who had married Guðrøðr's daughter, Affrica, may have played a critical role in John's successful conquest of the Kingdom of Ulaid. Guðrøðr died in 1187 and was succeeded by his eldest son, Rǫgnvaldr. Although Guðrøðr may have attempted to avert any succession disputes between his descendants, Rǫgnvaldr and his younger brother, Óláfr svarti, eventually fought each other over the throne, and the resulting conflict carried on into later generations.