Lulach I of Scotland (c. 1029- March 17, 1058), was king of Scotland between August 15, 1057 and March 17, 1058. He was the last king of the House of Alpin.

He appears to have been a weak king, and was indeed known as Lulach the Simple or Lulach the Fool. He does, however, have the distinction of being the first king of Scotland of whom there are coronation details available. He was crowned in August 1057 at Scone Abbey in Perthshire, Scotland.

Lulach was said to be the son of princess Gruoch of Scotland (Lady Macbeth), from her first marriage to Gillacomagnan the Earl of Moray, and thus the stepson of Macbeth. Following the death in battle of Macbeth in 1057, the king's followers placed Lulach in the throne, despite strong resistance from the Malcolm Canmore faction. Lulach ruled only for a few months before being assassinated and succeeded by Malcolm.