Laynez, Or Lainez, Diego, the second general of the society of Jesus, born at Almazan, Castile, in 1512, died in Rome, Jan. 19,1565. He received his master's degree in the university of Alcala in 1533, and in the same year went to Paris for the double purpose of completing his theological studies and of forming the acquaintance of Ignatius Loyola. (See Jesuits.) He was ordained priest in Venice, June 24, 1537, and in the following November was appointed by Paul III. to teach scholastic theology in the Sapienza college in Rome. He was afterward employed in a series of reformatory missions destined to check in upper Italy the spread of Protestant doctrines, and to revive faith and piety among the clergy and people. One of the results of his labors there was the foundation in 1542 of a Jesuit college in Padua. He appeared at the council of Trent in May, 1540, as one of the pope's theologians, opening and closing in this capacity every public discussion, and recapitulating the arguments on both sides. He labored during 1548 in reforming various dioceses in Sicily, founding schools, hospitals for the sick, and retreats for the aged and unprotected, as well as the college of Palermo. In 1550 he accompanied the Spanish expedition to Tunis, and on his return he was appointed provincial of his order in upper Italy. He opened the debates in the council of Trent, when it reassembled in 1551, and used his best endeavors to secure freedom to the Protestants invited to be present.

During repeated attacks of fever from which he suffered, the council suspended its sessions. In punishment of a fault of insubordination which he committed in 1551, he was ordered by Loyola to compose a complete summary of dogmatic theology. The manuscript still exists in Rome, but no one has been able to decipher the writing. After the death of Loyola in 1556, Laynez governed the order as vicar general till 1558, when he was unanimously chosen general. In 1559 twelve of the cardinals had resolved to elect him pope after Paul IV.; but their purpose was frustrated by his flight from Rome. In 1561 he went by order of the pope to the conference of Poissy, and in 1562 he was present again at the council of Trent, where he took a leading part. Laynez was conspicuous for his unwearied zeal in teaching; and he used his great influence in establishing free schools, colleges, and universities, and in extending the missionary enterprises of the Jesuits. He twice declined the dignity of cardinal. - Besides the work on theology already mentioned, he left several manuscript treatises on other subjects, all of which are equally illegible.

His life was written in French by Michel d'Esne (Donai, 1597).