Duke of Montblanc (Catalan: Duc de Montblanc, Spanish: Duque de Montblanc) is a noble Spanish title which since the 15th century has been preserved as one of the titles of the heir apparent to, first, the Aragonese crown and, later and currently, the Spanish. 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. When Martin became King of Aragon in 1396, the title returned to the crown.