St. Aloysius Gonzaga, (born March 9, 1568, Castiglione delle Stiviere, Republic of Venice [Italy]—died June 21, 1591, Rome; canonized 1726; feast day June 21), Italian Jesuit and patron saint of Roman Catholic youth.

Aloysius was the eldest of seven children born to Ferrante Gonzaga, marchese di Castiglione. Destined for a military career as a nobleman, he was educated at the ducal courts of Florence and Mantua and at the royal court of Madrid, where he was page to King Philip II's son Diego. However, in 1585 he resigned his inheritance and social status and entered the Society of Jesus (the Jesuit order) at Rome, where one of his spiritual directors was the renowned theologian St. Robert Bellarmine. Aloysius was noted for his asceticism and quickly volunteered to care for the sick and dying at a Jesuit hospital when plague broke out in Rome. Shortly before his ordination, he contracted the disease himself and died at age 23.

He was named patron of youth by Pope Benedict XIII in 1729, an action confirmed by Pope Pius XI in 1926.