Duke of Arjona (Spanish: Duque de Arjona) is a hereditary title in the Peerage of Spain, accompanied by the dignity of Grandee and granted in 1423 by John II to Fadrique Enríquez de Castilla, Count of Trastámara and a great-grandchild of Alfonso XI. It was rehabilitated by Alfonso XIII in 1902, in favour of Jacobo Fitz-James Stuart, 17th Duke of Alba, who was the heir of the House of Lemos, and by extension, of the Dukedom of Arjona, one of the oldest titles in Spain. The title makes reference to the town of Arjona, in the Province of Jaén.