In 1337, King Edward III established the Duchy of Cornwall via a royal charter for his son, Edward, Prince of Wales, also known as the "Black Prince." Edward would become the first Duke of Cornwall, and the charter outlined that the future Dukes of Cornwall will henceforth be given to be the eldest surviving son of the monarch and the heir to the throne.
If a woman was heir to the throne, however, she will not be Duchess of Cornwall, or if someone was heir to the throne that wasn't a son (i.e. a brother, grandson, or uncle), they would not be Duke of Cornwall. When there is no legitimate son of the sovereign, the duchy reverts to the Crown. The duchy owns about 50,000 hectares of land across 20 counties, and it was created with the explicit purpose of generating income for the heir to the throne.
In 2022, upon King Charles III's accession to the throne, Prince William became Duke of Cornwall, and Kate Middleton became Duchess of Cornwall. Unlike the Prince and Princess of Wales titles, the Cornwall titles are automatically inherited and restricted to the eldest son of a monarch. Therefore, some Dukes of Cornwall over the years held the title for just one day, or one year, depending on how long they lived as the oldest son of the monarch (and heir to the throne).
Starting with the Black Prince, a.k.a. Edward of Woodstock, all the way through Prince William, here are the 25 people who have held the Duke of Cornwall title throughout history: