heir apparent to the throne of Navarre (from 1428), who intrigued for both the Navarrese and Aragonese crowns.

The son of the future John II of Aragon and Blanche, daughter of Charles III of Navarre, who succeeded her father in 1425, Carlos was accepted as heir apparent by the Navarrese Cortes. On Blanche's death (1441) her testament was found to direct Carlos not to use the royal titles without his father's consent. John, who regarded his son with jealous animosity, withheld consent, but Carlos, for a time, governed Navarre as viceroy; later, however, John sent his second wife, Juana of Castile, to supervise the Navarrese government (1451), and civil war began between beaumonteses, who defended Prince Carlos' rights, and agramonteses, supporters of Juana. Defeated and disinherited, Carlos fled to the Neapolitan court of his uncle, Alfonso V of Aragon (1455), devoting himself to literary studies in Messina.

When Alfonso was succeeded in Aragon by John (1458), Carlos obeyed an order to return home and was enthusiastically received by the Catalans, who demanded his formal recognition as heir to the Aragonese throne. The intrigues of Queen Juana on behalf of her own son Ferdinand prevented this, and Carlos was imprisoned by his father (1460). The Catalans then rebelled (February 1461), forcing John II to proclaim Carlos his heir and governor of Catalonia (June). But the prince died, leaving John to cope with a general uprising of the Catalans, who believed—probably without reason—that Carlos had been murdered.