FERDINAND III. (1200-1252), usually known as Saint Ferdinand, was the son of Alphonse IX. of Leon, and of Berenguela, sister of Henry I. of Castile. On the death of Henry without issue in 1217, the just title of Blanche, the elder of the surviving sisters, was set aside and Berenguela procured the proclamation of Ferdinand. He rapidly secured the homage of the towns and the submission of the nobles, especially of the brothers Alvaro and Fernando de Lara. On the death of his father in 1230 he ultimately, though not without dispute, became king of Leon as well as of Castile, thus finally uniting the two kingdoms under one crown. Following up the advantage which had been gained for the Christian arms by his father and the allied kings in the great battle at Las Navas de Tolosa in 1212, he devoted all his energies to the prosecution of the Moorish var. Among his conquests may be mentioned those of Ubeda in 1234, of Cordova in 1236, of Jaen in 1245, and of Seville in 1248. He was planning an invasion of Africa when he died at Seville on the 30th of May 1252, leaving his kingdom to his eldest son Alphonso X. (Mouse el Sabio).

Though not canonized till centuries afterwards (by Clement X. in 1671), he came to be popularly known as el Santo from a very early period. Distinguished though he was for great military talent, he was still more remarkable for his religious zeal. Like his younger cousin Saint Louis of France, he was supremely a champion of the Catholic faith. It was not on the field of battle alone that his ardour was displayed. His Spanish panegyrists never fail to relate how it was his wont to assist in carrying wood for burning the followers of the Albigensian heresy, and how sometimes with his own royal hands he applied the torch to the pile.' While as a crusader be is hardly eclipsed by Louis, he contrasts very favourably with him as a sincere friend of learning. He was the original founder (1243) of the university of Salamanca, which his son and successor did so much to foster and encourage. He it was also who caused to be translated into the vulgar tongue the Fuero Juzgo (Forum Judicum) or code of Visigothic laws, which as collected and translated at his instance has the double interest of being one of the oldest extant specimens of Castilian prose, and also of being the foundation of Las Siete Partidas, the code for Christian Spain, which was finally drawn up by Alphonso the Wise.

His body now lies in the Capilla Real of Seville Cathedral, where it is exhibited as a relic on certain annual occasions (in May, August, and November). His day in the Spanish calendar is May 30.

See Mariana, Mist. Gen., XII. vii. - XIII. viii ; and compare Conde, Dominacion dc los Arabcs en Espalla, IV.