Alfonso I, Duke of Gandia

Alfonso de Aragón y Foix (1332 - Gandia, 5 March 1412) also called Alfonso I of Gandía "the old" and Alfonso IV of Ribagorza, was the eldest son of Count Peter of Ribagorza and Juana of Foix. He was the grandson of James II of Aragon and cousin of Pedro IV "the Ceremonious". He held the titles of Duke of Gandía (from 1399), Count of Denia (since 1355), Count of Ribagorza (from 1361), Marquis of Villena (since 1366), and first Constable of Castile.

He was a claimant to the Crown of Aragon in the succession crisis that followed the death of Martin of Aragon with no children. Alfonso claimed the crown as senior male-line descendant of James II. Alfonso died before the crisis was resolved by the Compromise of Caspe; his claim was inherited by his brother, Juan of Aragon and Foix.