Alfonso, Prince of Asturias (1453–1468)

Alfonso, Prince of Asturias (1453 – July 5, 1468), was the heir apparent to the throne of Castile during the reign of his half-brother, King Henry IV. He was the son of King John II of Castile and Isabella of Portugal.

Alfonso's parentage and legitimacy were questioned throughout his life, fueled by rumors surrounding the legitimacy of Henry IV's daughter, Joanna la Beltraneja. These doubts led to significant political instability in Castile. Opponents of Henry IV, including powerful nobles, used Alfonso as a figurehead to challenge Henry's rule.

In 1465, the League of Nobles deposed Henry IV in a staged ceremony known as the Farce of Ávila, proclaiming Alfonso as king. This marked the beginning of a civil war in Castile, pitting supporters of Henry IV against those of Alfonso.

Alfonso's brief reign, though disputed, was marked by intense political maneuvering and military conflict. He was supported by a faction of the nobility seeking greater autonomy and challenging Henry's policies. His death in 1468, likely from plague, unexpectedly altered the course of Castilian history.

After Alfonso's death, his supporters offered the crown to his sister, Isabella, who ultimately succeeded in claiming the throne after Henry IV's death in 1474, leading to the War of the Castilian Succession against Joanna la Beltraneja. Alfonso's role as a claimant to the throne and a symbol of noble opposition to Henry IV played a crucial part in the events leading to Isabella's ascension.