Ferdinand I named Ferdinand of Antequera and also the Just was king of Aragon, Valencia, Majorca, Sardinia and (nominal) Corsica and king of Sicily, duke (nominal) of Athens and Neopatria, and count of Barcelona, Roussillon and Cerdanya (1412–1416). He was also regent of Castile (1406–1416). He was the first Castillian ruler of the Crown of Aragó and his dynasty came to unify the Iberian peninsula under Castillian rule.

The Kingdom of Aragon was a medieval and early modern kingdom on the Iberian Peninsula, corresponding to the modern-day autonomous community of Aragon, in Spain. It should not be confused with the larger Crown of Aragon, which also included other territories—the Principality of Catalonia, the Kingdom of Valencia, the Kingdom of Majorca, and other possessions that are now part of France, Italy, and Greece—that were also under the rule of the King of Aragon, but were administered separately from the Kingdom of Aragon.