HENRY IV. (1425-1474), king of Castile, surnamed el Impotente (the impotent) and sometimes el Liberal (the spendthrift), the eldest son of John II. by his first wife Maria of Aragon, was born at Valladolid on January 6, 1425. As prince of Asturias he took a prominent and generally an unfilial part in most of the disturbances of his father's reign; in 1445 a pitched battle between the king and the prince was prevented only at the last moment by the in-tervention of the clergy and some of the nobles ; and peace was not finally secured until 1450 when Pope Nicholas V. issued his bull of excommunication against all those in the peninsula who, by perplexing the affairs of the sovereign, were disastrously helping the cause of the infidels. In 1440 Henry had in accordance with a treaty signed in 1436 been united to Blanche of Aragon; but this marriage, which had not been happy and which had given cause to many scandalous reports, he dissolved in 1453 shortly before his accession to the throne on his father's death in July of that year. He began his reign with a great show of energy against the Moors; but the boldness of his intentions con-trasted strangely with the feebleness of his execution; and the unsatisfactory character of the results attained tended greatly to bring to a head the discontent which his indolent inattention to home affairs, his reckless extravagance, and the disorders of his private life had not failed to create. In 1465 occurred at Avila the extraordinary scene, so often described, of the king's deposition in favour of his brother Alphonso; this was followed in 1468, shortly after Alphonso's death, by the election of his sister Isabella, who, however, declined to accept the proffered crown. In the same year Henry was forced to repudiate his wife Joanna of Portugal and to disinherit her daughter Juana (la Beltraneja) whom he had unsuccessfully attempted to put forward as also his ; and thus the succession became fixed in favour of Isabella, who was married to Ferdinand of Aragon in the following year. Henry died at Madrid on December 12, 1474.

For the events of the reign of Henry IV. the contemporary authorities are Alonso de Falencia and Diego Henriquez del Castillo, each of whom has left a Cronica del Rey Don Enrique Quarto; the best and at the same time the most accessible modern English account is to be found in Prescott's History of the Reign of Ferdinand and Isabella, part i., chaps, iii. and iv.