General from 1558 to 1565

Diego was born in 1512 at Almazan, Castile in Spain. In 1534 he became one of Ignatius' first companions at the University of Paris. He had studied the humanities at Soria and Sigüenza and Alcala in Spain, but felt the need of the broadening effects which could be received at the University of Paris. He had found more than he had expected when he encountered his fellow-student Ignatius of Loyola, a fellow Spaniard and one who already had a reputation for spiritual direction. After making the Spiritual Exercises under the direction of Ignatius, Diego gave himself completely and whole-heartedly to the little group who had formed around Ignatius. With them he pronounced his vows with six others in the little chapel of a convent on Montmartre and would remain a close companion and collaborator of Ignatius for the rest of his life. With the group he was ordained to the priesthood in Venice while on the way to Rome and later, with them, pronounced his formal vows of Poverty, Chastity, and Obedience in the Chapel of Our Lady in St. Paul's basilica in Rome. By his long association and by the confidence Ignatius had in him, he was trusted with positions of authority. Ignatius depended upon Lainez for help in areas where he, himself, did not have the time or no longer had the endurance. Lainez was posted to the Council of Trent at the request of the Pope himself and as a very prominent theologian was referred to by the Pope as one of the most outstanding diplomats and churchmen of his time.

When Ignatius took sick and finally died, Jesuits in Rome had to assemble and reassess their effectiveness and what the future would hold for them with Ignatius no longer there to advise and guide them. Because of politics and national rivalries, it was two years before the Fathers could be assembled for the meeting they would call a "Congregation." When the day arrived for the assembly where they would discern in prayer and reflection who of their number should take over the authority and burdens that Ignatius, the 1st General, had left behind, the Companions assembled in what is known as the First General Congregation, in the room where Father Ignatius had died. It was a small room, but could easily accommodate the twenty fathers who had to make this momentous decision for the early Company of Jesus. The congregation was held between June 19 and September 10, 1558 and Lainez, only 46 years old at the time, was elected by thirteen votes out of the 20.

The term of his Generalate lasted for six years and six months, from July 2, 1558 until January 19, 1565. He continued faithfully the line traced out by Ignatius because he knew the mind of Ignatius so well.

When he died on January 19, 1565 he was almost 53 years old having spent his time as General in consolidating the Constitutions as written by Ignatius.

The Jesuits throughout Spain requested that his body be sent back to his home to rest among them as encouragement and remembrance. It was so done and his body was interred in the Jesuit Church in Madrid. There his bones rested for almost four hundred years until in 1930 when civil unrest, anti-Catholic sentiment and Masonic influences in the Spain of those years preceding the Spanish Civil War of the mid-thirties, the Jesuit church was torched by a mob and it burned to the ground. What remained of Lainez' bones—only a handful of ashes—were re-interred in the south wall of the present Jesuit Church on Maldonado, where they rest today behind a plaque attesting to their authenticity and the place once held by Lainez in the Society of Jesus.