CASTRO, JoIco DE (1500-1548), called by Camoens Castro Forte, fourth viceroy of the Portuguese Indies, was the son of Alvaro de Castro, civil governor of Lisbon. A younger son, and destined therefore for the church, he became at an early age a brilliant humanist, discover-also a profound capacity for mathematics. The latter he studied under Pedro Nunez, in company with the Infante Dom Luis, son of Emmanuel the Great, with whom he contracted a life-long friendship. At eighteen he went to Tangiers, where he was dubbed knight by Duarte de Menezes the governor, and where he remained several years. In 1535 he accompanied Dom Luis to the siege of Tunis, where he had the honour of refusing knighthood and reward at the hands of the great emperor Charles V. Returning to Lisbon, he received from the king the small commandership of She Pablo de Salvaterra in 1538. He was exceedingly poor, but his wife Lenor de Coutinho, a noble Portuguese lady, the exact date of whose marriage with him is not known, admired and appreciated her husband sufficiently to make light of their poverty. Soon after this he left for the Indies in company with his uncle Garcia de Noronha, and on his arrival at Goa enlisted among the arentureiros, " the bravest of the brave, " told off for the relief of Diu. In 1540 he served on an expedition under Estabao de Gama, by whom his son, Alvaro de Castro, a child of thirteen, was knighted, out of compliment to him. Returning to Portugal, Joao de Castro was named commander of a fleet, in 1543, to clear the European seas of pirates ; and in 1545 he was sent, with six sail, to the Indies, in the room of Martin de Souza, who had been dismissed the viceroyalty. The next three years were the hardest and most brilliant, as they were the last, of this great man's life, - years of battle and struggle, of glory and sorrow, of suffering and triumph. Valiantly seconded by his sons (one of whom, Fernao, was killed before Diu) and by Joao Mascarenhas, Joao de Castro achieved such popularity by the overthrow of Mahmoud, king of Cambodia, by the relief of Diu, and by the defeat of the great army of Adhel Khan, that he could contract a very large loan with the Goa merchants on the simple security of his moustache. These great deeds were followed by the capture of Broach, by the complete subjugation of Malacca, and by the passage of Antonio Moniz into Ceylon ; and in 1517 the great captain was appointed viceroy by Joao III,, who had at last accepted him without mistrust. He did not live long to fill this charge, expiring in the arms of his friend, St Francis Xavier, 6th June of the following year. He was buried at Goa, but his remains were afterwards exhumed and conveyed to Portugal, to be reinterred under a splendid monument in the convent of Bemfica.

See Jacinto Freire de Andrade, Vida de D. foal de Castro, Lisbon, 1651, - English translation, by Sir Peter Wyche, 1664; Joao he Barns, Decade secunda da Asia, bk. Roteiro de Dom Joam, de Castro, Paris, 1833. The last is important as fixing the position of Joao de Castro among geographers.