The Duchy of Braganza (Portuguese: Ducado de Bragança) has been the fief of an important Portuguese noble family: the House of Braganza, and is one of the most important Dukedoms of Portugal.

After the accession of the House of Braganza to the Portuguese throne in 1640, following the House of Habsburg, the heir to the throne of Portugal was styled as the Duke of Braganza (see that article for further developments of the dukedom) together with Prince of Brazil, and later Prince Royal of Portugal.

Legend says that his wife, Leonor of Guzman, daughter of the duke of Medina-Sidónia, urged him to accept the offer saying, I'd rather be Queen for one day than duchess for a lifetime.

He accepted the leadership of the rebellion, which was successful, and was acclaimed John IV of Portugal on December 1, 1640.

After the accession of the Braganzas to the throne, the duchy was linked to the Crown and the Duke of Braganza became the traditional title of the heir to the Crown, together with or alternate to Prince of Beira, much as Prince of Wales is in the United Kingdom.