Alfonso de Ulloa (1529 – 1570) was a Spaniard living in Venice, who published and translated works from Spanish to Italian.
His father had putatively fought for Emperor Charles V in the 1541 expedition to Algiers, and died circa 1540 in a voyage of exploration of the American Pacific.
In that service, it is almost certain that Alfonso would have had contact with Mendoza's librarian, Arnoldus Arlenius, who also worked at translating Ancient Greco-Roman classics.
In 1552, the Gioliti firm published a translation by Ulloa into Spanish of Girolamo Muzio's Il Duello (The Duel).
He was imprisoned in 1567 in Venice, putatively for falsifying an official permission from the Council of Ten allowing him to publish a book in Hebrew.