Jerónimo Osório (1506 – August 20, 1580) was a Portuguese historian, a native of Lisbon and son of the Ouvidor Geral of India.
In 1519 his mother sent him to Salamanca to study civil law, and in 1525 he went on to Paris to study philosophy, and there became intimate with Peter Faber, one of the founders of the Society of Jesus. Returning to Portugal, Osório next proceeded for theology to Bologna, where he made such a name that King John III. invited him in 1536-1537 to lecture on scripture in the reorganized university of Coimbra. He returned to Lisbon in 1540, and acted as secretary to Prince Luís, and as tutor to his son, the prior of Crato, obtaining also two benefices in the diocese of Viseu. In 1542 he printed in Lisbon his treatise De nobilitate. After the death of Prince Luís in 1553, he withdrew from court to his churches.
He was named archdeacon of Évora in 1560, and much against his will became bishop of Silves in 1564. The Cardinal Prince Henry, who had bestowed these honors, desired to employ him at Lisbon in state business when King Sebastian took up the reins of power in 1568, but Osório excused himself on the ground of his pastoral duties, though he showed his zeal for the commonwealth by writing two letters, one in which he dissuaded the king from going to Africa, the other sent during the latter's first expedition there, in which he called on him to return to his kingdom. Sebastian looked with disfavor on opponents of his African adventure, and Osório found it prudent to leave Portugal for Parma and Rome on the pretext of a visit ad limina. His scruples regarding residence, and the appeals of the King and the Cardinal Prince, prevented him enjoying for long the hospitality of Pope Gregory XIII., and he returned to his diocese and died at Tavira on 20 August 1580.
An exemplary prelate, a learned scholar and an able critic, Osório gained a European reputation by writing in Latin, then the lingua franca of the studious throughout Christendom, and the perfection of his prose style caused him to be named by contemporaries the Portuguese Cicero. His well-stocked library was carried off from Faro when the earl of Essex captured the town in 1596, and many of the books were bestowed on the Bodleian at Oxford.
His principal works written in Latin include:
Osorio's book was turned into Portuguese by Francisco Manoel de Nascimento, into French by J. Crispin 2 vols., Geneva, 1610), and an English paraphrase in 2 vols. by J. Gibbs came out in London in 1752. His Opera omnia were published by his nephew (4 vols., Rome, 1592). Two of his polemical treatises have been translated into English, his Epistle to Elizabeth Queen of England by R. Shacklock (Antwerp, 1565), and his Confutation of M. W. Haddon by John Fenn, against Walter Haddon (Louvain, 1568). His Portuguese epistles, including the two before mentioned, were printed in Lisbon in two editions in 1818 and 1819, and in Paris in 1859. For his biography see Obras de D. F. A. Lobo, bishop of Vizeu, i. 293-301