Duke of Cornwall is a title in the Peerage of England, traditionally held by the eldest son of the reigning British monarch, previously the English monarch. The Duchy of Cornwall was the first duchy created in England and was established in a royal charter in 1337 by King Edward III. Prince William became Duke of Cornwall following the accession of his father, King Charles III, to the throne in 2022, and his wife, Catherine, became Duchess of Cornwall.

The Duchy of Cornwall is one of two royal duchies in England, the other being the Duchy of Lancaster. The eldest son of the reigning British monarch obtains possession of the duchy and the title of Duke of Cornwall at birth or when his parent succeeds to the throne, but may not sell assets for personal benefit and has limited rights and income while a minor.