ISABELLA (1451-1504), surnamed la Catolica, "the Catholic," queen of Castile, was the second child and only daughter of John II. of Castile by his second wife Isabella, granddaughter of John I. of Portugal (thus being through both parents a descendant of John of Gaunt), and was born at Madrigal on the 22nd of April 1451. On the death of her father, who was succeeded by her brother Henry IV. (1454), she was withdrawn by her mother to Arevalo, where her early education was conducted in the deepest seclusion; in 1462, however, along with her uterine brother Alphonso, she was removed by Henry to the court, where she showed a remarkable example of staidness and sobriety. Already more than one suitor had made application for her hand, Ferdinand of Aragon, who ultimately became her husband, being among the number; for some little time she was engaged to his elder brother Charles, who died in 1461. In her thirteenth year her brother promised her in marriage to Alphonso of Portugal, but she firmly refused to consent; her resistance seemed less likely to be effectual in the case of Pedro Giron, grand master of the order of Calatrava and brother of the marquis of Villena, to whom she was next affianced, when she was delivered from her fears by the sudden death of the bridegroom while on his way to the nuptials in 1466. After an offer of the crown of Castile, made by the revolutionary leaders in the civil war, had been declined by her, she was in 1468 formally recognized by her brother as lawful heir, after himself, to the united crowns of Castile and Leon. New candidates for her hand now appeared in the persons of a brother of Edward IV. of England (probably Richard, duke of Gloucester), and the duke of Guienne, brother of Louis XI., and heir presumptive of the French monarchy. Finally however, in face of very great difficulties, she was married to Ferdinand of Aragon at Valladolid on the 19th of October 1469. Thence forward the fortunes of Ferdinand and Isabella were inseparably blended. For some time they held a humble court at Dueñas, and afterwards they resided at Segovia, where, on the death of Henry, she was proclaimed queen of Castile and Leon (December 13, 1474). Spain undoubtedly owed to Isabella's clear intellect, resolute energy and unselfish patriotism much of that greatness which for the first time it acquired under "the Catholic sovereigns." The moral influence of the queen's personal character over the Castilian court was incalculably great; from the debasement and degradation of the preceding reign she raised it to being "the nursery of virtue and of generous ambition." She did much for letters in Spain by founding the palace school and by her protection of Peter Martyr d'Anghiera. The very sincerity of her piety and strength of her religious convictions led her more than once, however, into great errors of state policy, and into more than one act which offends the moral sense of a more refined age: her efforts for the introduction of the Inquisition into Castile, and for the proscription of the Jews, are outstanding evidences of what can only be called her bigotry. But not even the briefest sketch of her life can omit to notice that happy instinct or intuition which led her, when all others had heard with incredulity the scheme of Columbus, to recall the wanderer to her presence with the words, "I will assume the undertaking for my own crown of Castile, and am ready to pawn my jewels to defray the expenses of it, if the funds in the treasury should be found inadequate." She died at Medina del Campo on the 24th of November 1504, and was succeeded by her daughter Joanna "la loca" (the "Crazy") and her husband, Philip of Habsburg.
See W. H. Prescott, History of the Reign of Ferdinand and Isabella (1837), where the original authorities are exhaustively enumerated; and for later researches, Baron de Nervo, Isabella the Catholic, translated by Lieut.-Col. Temple-West (1897).