William Cavendish, 5th Duke of Devonshire, KG (14 December 1748 – 29 July 1811), was a British nobleman, aristocrat, and politician. He was the eldest son of William Cavendish, 4th Duke of Devonshire, by his wife, the heiress Lady Charlotte Boyle, suo jure Baroness Clifford, who brought in considerable money and estates to the Cavendish family. He was invited to join the Cabinet on three occasions, but declined each offer. He was Lord High Treasurer of Ireland and Governor of Cork.