Macbeth (Gaelic for "Son of Life") c. 1005–August 15, 1057 was the king of Scotland from August 14, 1040 to August 15, 1057 and the last Celtic king of Scotland.

He was the son of Dovada, Malcolm II's eldest daughter, and in some eyes, including his own, had a better claim to the throne than Malcolm II's chosen successor Duncan I, who was the son of Malcolm II's second daughter Bethoc. His political alliances were improved in 1032, when he married Gruoch — better known to history as Lady Macbeth, a granddaughter of Kenneth III of Scotland, and daughter of the prince Bodhe.

Macbeth formed an alliance with Thorfinn, Earl of Orkney, son of Malcolm II's youngest daughter, and took up arms against Duncan. Duncan died fighting them in battle near Elgin on August 14, 1040.

Macbeth was a strong king and ruled over a kingdom stable enough for him to be able to leave for several months on a pilgrimage to Rome. He instituted a new form of law and order in Scotland. His reign was noted as a time of prosperity. However, in 1054, Malcolm Canmore, Duncan's son, began his campaign for the throne with the assistance of Siward, Earl of Northumbria, by capturing the south of Scotland. Macbeth was killed by Malcolm's forces at a battle near Lumphanan and the throne passed to Macbeth's stepson, Lulach, in August, 1057.

Macbeth was buried on Iona, the traditional burial place of Scottish Royalty at that time. William Shakespeare's play Macbeth is loosely inspired by his life.