Sir Robert Ayton (1570 - 1638) was a Scottish poet.

He was the son of Ayton of Kinaldie in Fife. After graduating at St. Andrews, he studied law at Paris, became ambassador to the Emperor, and held other court offices.

He appears to have been well-known to his literary contemporaries in England. He wrote poems in Latin, Greek, and English, and was one of the first Scots to write in the English language. His major work was Diophantus and Charidora .

Inconstancy Upbraided is regarded as the best of his short poems. He is credited with a little poem, Old Long Syne , which probably suggested Robert Burns's famous Auld Lang Syne.