Nasi, Joseph (c.1504–79) Jewish leader. Born João Miguez, son of a Portuguese physician of New Christian (i.e. Jewish) origin, he left Lisbon to study at the university of Louvain (1537), began working for bankers in Antwerp, and in 1547 left for the east, passing through France and Venice. In 1554 he was in Istanbul, where he formally became a Jew and changed his name. Adopted as an adviser by the sultan Selim II because of his great knowledge of western Europe, he obtained important trading privileges.