Alexander III ruled Scotland as king from September 1249 to March 1286. He was the son of Alexander II and Mary de Coucy and became king at the age of eight when his father died.
During his minority rule was disputed between parties led by the earl of Menteith (a member of the Comyn family who themselves would claim a right to the throne some half-century later) and the justiciar, Alan Duward.
At the age of 10 Alexander was married to Margaret, daughter of Henry III of England. Henry demanded homage from Alexander for his kingdom, but Alexander refused.
On taking up his majority in 1262, Alexander made it clear that tyhe first political priority in his mind was to complete his father's project to liberate the Western Isles from Norse influence. He formally claimed the Isles from the Norwegian king Haakon, who rejected the claim and launched an invasion the next year. Haakon sailed to Arran and Alexander offered negotiations. He, however, protrated these until the autumn and when Haakon set out for home storms damaged many of his ships. A brief battle, at Largs, in October, was inconclusive but Haakon died on his voyage home and in 1266 his successor, Magnus ceded the Isles and the Isle of Man to Alexander for cash, leaving Norway with only Orkney and Shetland. It is, however, doubtful if the Anglo-Norse lords of the Isles paid any real attention to the change of nominal overlord -- they had long maintained a dignified and piratical attitude of independence from any control.
Princess Margaret died in 1274 but by then Alexander and she had had three children, a daughter, Margaret, who married Eirik of Norway, and two sons, Alexander and David.
But, in the event all three were to pre-decease their father between 1281 and 1283, leaving the succession uncertain. Alexander induced the Estates, the Scots Parliament, to recognise as heir-presumptive his grand-daughter Margaret, the 'Maid of Norway', and in 1285 he remarried, to Yolanda of Dreux, in the hope she could give him a male heir. But 5 months later, before this could happen, he died, from a fall from his horse and a cliff, and the three-year old girl became ruler of a land she had never seen.
Alexander's reign became remembered as a golden age: apart from the small war with Norway, he had kept Scotland and Scotsmen out of war, and had kept English claims to the northern kingdom at bay without arms. He had supported trade, which kept his revenues healthy, and he had maintained law and order, encouraged building and commerce and sought to see his people properly educated. His death robbed Scotland of a good king, and would eventually lead to instability, English interference, war, and two new Royal Houses.