Duke of Devonshire is a title in the Peerage of England held by members of the Cavendish family. This branch of the Cavendish family has been one of the richest and most influential aristocratic families in England since the 16th century, and has been rivalled in political influence perhaps only by the Marquesses of Salisbury and the Earls of Derby.
History
Although in modern usage the county of Devon is now rarely called 'Devonshire', the title remained 'Duke of Devonshire'. Despite the title of the dukedom and the subsidiary title, the earldom of Devonshire, the family estates are centred in Derbyshire. It should not be confused with the earlier title, Earl of Devon.
Uniquely, every Duke of Devonshire has been made a Knight of the Garter, except the present one (so far).