Donald I (Donald mac Alpin) (c812-863) was King of Alba (Scotland) from 858-863. He was the younger son of Alpin II of Dalriada and succeeded his brother, King Kenneth mac Alpin, to the throne upon his death.

Described before as the wanton son of the foreign woman, Donald had a short term as king. He established an ancient corpus of laws and rights (known as the laws of Aed, or Aedh) that apparently included the custom of tanistry. According to this custom, the successor of a king was elected during his lifetime from the eldest and worthiest of his kin, often a collateral (brother or cousin) in preference to a descendant (son). During Donald's reign, his nephew, Constantine I, was chosen to succeed him following his death. The custom of tanistry lasted until the reign of Malcolm II.

Uncertainty exists about the circumstances of his death in 863. He either died at a battle in Scone, Perthshire or peacefully in his palace at Kinn Belachoir. He died unmarried and childless. It is not known where he was buried.

Preceded by: Kenneth I

King of Scots

Succeeded by: Constantine I