Spanish Humanist. He and his twin brother, Alfonso, were members of an influential intellectual family that played significant roles in the religious, political, and literary life of Spain and its empire.

Juan studied under Spain's leading Humanists and developed religious views that closely followed the ideas of Erasmus of Rotterdam, with whom both he and his brother maintained a correspondence. His work Diálogo de la doctrina cristiana (1529; “Dialogue on Christian Doctrine”) was not well received by the Inquisition, and Valdés found it prudent to leave Spain. Accepting a post from the emperor Charles V, he spent the rest of his life in Italy but wrote in Spanish for his Italian public. The Diálogo de la lengua (c. 1535; “Dialogue on the Language”), which circulated only in manuscript until the 18th century, treated of Spanish style and language with that blend of wit, grace, learning, and common sense that characterizes Humanism at its best.