fifth and youngest general of the Society of Jesus, considered by many to have been the order's greatest leader. The youngest son of the Duke of Atri, he joined the order in 1567. Shortly after completing his studies he was appointed provincial superior of Naples and then of Rome.

He was elected general in 1581, and his major political achievement occurred at the Jesuits' fifth General Congregation (1593–94). He succeeded in overcoming the efforts of some Spanish Jesuits (Jesuit)—supported at first by King Philip II of Spain—to introduce modifications in the Institute of the Society of Jesus and to obtain a privileged status for the Spanish provinces.

Aquaviva's rule was marked by the rapid growth of the order from about 5,000 to more than 13,000 members and from 21 to 32 provinces, with the number of colleges reaching 372. His practical legislation strengthened the society and made it more efficient in its numerous foreign missions and colleges. He promoted the use of the Spiritual Exercises of St. Ignatius Loyola for the clergy and laymen. He encouraged the order's theologians and spiritual writers to more profound investigation and to publication. He organized the first scholarly writing of the history of the order and the compilation of annual reports of all the provinces (Litterae Annuae).

In the Constitutions of the order, Ignatius had indicated only in outline the Jesuit system of education. The fourth General Congregation, which had elected Aquaviva general, entrusted him with the task of drawing up a practical code of education for its schools. This work, Ratio atque institutio studiorum (“The Reason and Establishment of Studies”), was first published in 1586, at which time it was distributed to Jesuit schools for criticism and revision. The definitive text (1599) unified Jesuit teaching throughout the world, yet allowed for adaptation to local needs. His work strengthened the order internally and guided its external relations. He successfully furthered the apostolate of the Roman Catholic Church under eight popes, from Gregory XIII to Paul V.