Luigi Gonzaga (Aloysius is the Latin form of Gonzaga's given name) was born in the family’s castle in Castiglione delle Stiviere. He was the oldest son of the Ferdinando Gonzaga.
His father assumed that he would become a soldier, as the family was constantly involved in the frequent minor wars in the area. His military training started at an early age, but he also received an education in languages and other subjects. In 1577, at age 8, he was sent to Florence with his younger brother Ridolfo, to serve at the court of Grand Duke Francesco I de' Medici and to receive further education. While there, he fell ill with a disease of the kidneys, which was to trouble him throughout his life. While he was ill, he took the opportunity to read about the saints and to spend much of his time in prayer. He is said to have taken a private vow of chastity at the age of 9. In November 1579, the brothers were sent to the Duke of Mantua. Aloysius was shocked by the violent and frivolous life-style he encountered there.
In 1580, he returned to Castiglione. There, he met Cardinal Charles Borromeo in July of the same year. The cardinal found out that Aloysius had not yet received his first holy communion, and gave this to him on 22 July 1580. After reading a book about Jesuit missionaries in India, he felt strongly that he wanted to become a missionary himself. He started practicing by giving catechism classes to young boys in Castiglione in the summers, and by frequently visiting the Capuchins and Barnabites in Casale Monferrato, the capital of the Gonzaga-ruled Duchy of Montferrat where the family spent the winter. He also adopted an ascetic life-style.
The family was called to Spain in 1581, to assist Empress Mary of Austria. They arrived in Madrid in March 1582, and Aloysius and Ridolfo became pages for the infante don Diego, Prince of Asturias (1575-82). He then started thinking in earnest about joining a religious order. He had considered joining the Capuchins, but he had a Jesuit confessor in Madrid, and decided to join that order. His mother agreed to his request to join the Jesuits, but his father was furious. In July 1584, one and a half years after the infante's death, the family returned to Italy. Aloysius still wanted to become a priest, and several members of his family worked hard to persuade him to change his mind. When they realized that there was no way to make him give up his plan, they tried to persuade him to become a secular priest, and to arrange for a bishopric for him. If he became a Jesuit he would renounce any right to income from property or status in society. His family was afraid of this, but their attempts to persuade him not to join the Jesuits failed; Aloysius was not interested in higher office and still wanted to become a missionary.
In November 1585, Aloysius gave up all rights of inheritance, and this was confirmed by the emperor. He went to Rome and, because of his noble birth, gained an audience with Pope Sixtus V. On 25 November 1585 he was accepted into the Jesuit Roman noviciate by the order's general, Claudius Acquaviva. He was asked to moderate his asceticism somewhat, as it disrupted his relationship with the other novices; they found it difficult to speak with him when he isolated himself. In part, this may also have been caused by his upbringing, where he had never learned to relate to people outside the court.
His health continued to cause problems. In addition to the kidney disease, he also suffered from a skin disease, chronic headaches and insomnia. He was sent to Milan for studies, but after some time he was sent back to Rome because of his health. On November 25, 1587, he took the three religious vows of chastity, poverty and obedience. In February and March 1588, he received the lower ordinations, and started studying theology to prepare for the priesthood. In 1589, he was called to Mantua to mediate between his brother Ridolfo and the Duke of Mantua. He returned to Rome in May 1590. Later that year, he had a vision in which the Archangel Gabriel told him that he would die within a year.
In 1591, a plague broke out in Rome. The Jesuits opened a hospital for the stricken, and Aloysius volunteered to work there. He was allowed to work in a ward where there were no plague victims, as they were afraid to lose him. As it turned out, a man on his ward was infected, and on 3 March 1591 Aloysius showed the first symptoms of being infected. It seemed certain that he would die in a short time, and he was given Extreme unction (Anointing of the Sick). To everyone's surprise, he recovered, but his health was left worse than ever. While he was ill, he spoke several times with his confessor, cardinal Robert Bellarmine. Aloysius had another vision, and told his confessor that he would die on the octave of Corpus Christi. On that day, which fell on 21 June, he seemed very well in the morning, but insisted that he would die before the day was over. Cardinal Bellarmine gave him the sacraments, and recited the prayers for the dying.
Aloysius was buried in the Church of the Annunciation in Rome. His name was changed to Robert before his death, in memory of his confessor. Many people considered him to be a saint soon after his death, and his mortal remains were moved to the Sant'Ignazio church in Rome, where they now rest in an urn of lapis lazuli in the Lancelotti Chapel. His head was later translated to the basilica bearing his name in Castiglione delle Stiviere. He was beatified only 14 years after his death by Pope Paul V, on 19 October 1605. On 31 December 1726, he was canonized together with another Jesuit novice, Stanislaus Kostka, by Pope Benedict XIII. The same pope declared him to be the patron saint of young students in 1729. In 1926, he was named patron of Christian youth by Pope Pius XI. Because of the manner of his death, he has always been considered a patron of plague victims. In recent years, many have felt it proper to extend this to include AIDS victims.
In art, he is shown as a young man wearing a black cassock and white rochet, or as a page. His attributes are a lily, referring to innocence; a cross, referring to piety and sacrifice; a skull, referring to his early death; and a rosary, referring to his devotion to the Virgin Mary.