The Society of Jesus (Latin: Societas Iesu; abbreviated S.J. or SJ), also known as the Jesuits (; Latin: Iesuit), is a religious order of the Catholic Church headquartered in Rome. It was founded by Ignatius of Loyola and six companions with the approval of Pope Paul III in 1540. The society is engaged in evangelization and apostolic ministry in 112 nations. Jesuits work in education, research, and cultural pursuits. Jesuits also give retreats, minister in hospitals and parishes, sponsor direct social ministries, and promote ecumenical dialogue.

The Society of Jesus is consecrated under the patronage of Madonna Della Strada, a title of the Blessed Virgin Mary, and it is led by a Superior General. The headquarters of the society, its General Curia, is in Rome. The historic curia of Ignatius is now part of the Collegio del Ges attached to the Church of the Ges, the Jesuit mother church.

Members of the Society of Jesus are expected to accept orders to go anywhere in the world, where they might be required to live in extreme conditions. This was so because Ignatius, its leading founder, was a nobleman who had a military background. Accordingly, the opening lines of the founding document declared that the society was founded for "whoever desires to serve as a soldier of God, to strive especially for the defence and propagation of the faith, and for the progress of souls in Christian life and doctrine". Jesuits are thus sometimes referred to colloquially as "God's soldiers", "God's marines", or "the Company". The society participated in the Counter-Reformation and, later, in the implementation of the Second Vatican Council.

Ignatius of Loyola, S.J. (born Iñigo López de Oñaz y Loyola; Basque: Ignazio Loiolakoa; Spanish: Ignacio de Loyola; Latin: Ignatius de Loyola; c. 23 October 1491 – 31 July 1556), venerated as Saint Ignatius of Loyola, was a Spanish Catholic priest and theologian, who, with Peter Faber and Francis Xavier, founded the religious order of the Society of Jesus (The Jesuits), and became the first Superior General of the Society of Jesus, in Paris, in 1541. He envisioned the purpose of the Society of Jesus to be missionary work and teaching. Unlike members of other religious orders in the church who take the vows of chastity, obedience and poverty, members of the society, Jesuits, also take a fourth vow of obedience to the Pope, to engage in projects ordained by the pontiff. Jesuits were instrumental in leading the Counter-Reformation.As a former soldier, Ignatius paid particular attention to the spiritual formation of his recruits and recorded his method in the Spiritual Exercises (1548). In time, the method has become known as Ignatian spirituality.

Ignatius of Loyola was beatified in 1609 and canonized saint, on 12 March 1622. His feast day is celebrated on 31 July. He is the patron saint of the Basque provinces of Gipuzkoa and Biscay as well as of the Society of Jesus. He was declared patron saint of all spiritual retreats by Pope Pius XI in 1922.