Spanish military leader renowned for his exploits in southern Italy.

Fernández was sent to the Castilian court at the age of 13 and distinguished himself in the fighting following Isabella I's accession (1474), and he played an increasingly important role in the war against the Muslim kingdom of Granada. He was one of the two commissioners who conducted the final negotiations for the surrender of Granada (1492).

In 1495 Isabella gave him command of an expedition in support of the Aragonese king of Naples against the French in Italy. Fernández quickly achieved success on behalf of his ally and at the request of Pope Alexander VI defeated a lingering French garrison in Ostia (March 1497). In 1500 he was sent to Italy in command of a larger force, for cooperation with Louis XII of France against the Ottoman Turks but also to be ready to counter French ambitions in regard to Naples. Together with the Venetians, he captured (December 1500) the strongly held island of Cephalonia. The immediate Turkish threat having been removed, a secret agreement was signed by the king of France and Ferdinand dividing the Kingdom of Naples between them. The French disputed and overran the agreed lines of the division and by 1502 were engaged in a war with the Spaniards under Fernández in which he won the striking victories of Cerignola, Monte Cassino, and the Garigliano. In this last battle Fernández brought about the surrender of far larger and more heavily armed forces by an unexpected night attack (Dec. 27, 1503) across the flooded estuary by means of pontoons.

Ferdinand recalled Fernández from the viceroyalty of Naples in 1507 but again gave him a command following a French threat after the Battle of Ravenna (1512).