The title is specifically that of the heir to the Principality of Catalonia, part of the Crown of Aragon.
The Duchy of Montblanc was created by John I of Aragon when he granted it to his brother Martin on January 6, 1387.
Since then, kings have bestowed "Duke of Montblanc" as a nonhereditary title, usually upon one of their sons.
After the War of the Spanish Succession (1700–1714), the victorious Philip V of Spain disestablished all the statuses and constitutions of the Crown of Aragon, including the Duchy of Montblanc.
Since 19 June 2014, the title has been reserved for Felipe's daughter Leonor, Princess of Asturias, as heiress presumptive to the Spanish crown.