Ferdinand I (Spanish: Fernando I) called of Antequera and also the Just (or the Honest) 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).
Born at Medina del Campo, he was the younger son of King John I of Castile and Eleanor of Aragon.
In 1406, upon the death of his elder brother, King Henry III of Castile, Ferdinand declined the Castilian crown and instead, with Henry's widow Catherine of Lancaster, became coregent during the minority of his nephew John II of Castile. In this capacity he distinguished himself by his prudent administration of domestic affairs.
After Ferdinand's maternal uncle, King Martin I of Aragon (Martin II of Sicily), died without surviving legitimate issue, Ferdinand was chosen King of Aragon in 1412 to succeed him in the Compromise of Caspe.
The most notable accomplishment of his brief reign was his agreement in 1416 to depose the Antipope Benedict XIII, thereby helping to end the Western Schism, which had divided the Roman Catholic Church for nearly 40 years.