Francis Xavier (born Francisco de Jasso y Azpilicueta; Latin: Franciscus Xaverius; Basque: Frantzisko Xabierkoa; French: Franois Xavier; Spanish: Francisco Javier; Portuguese: Francisco Xavier; 7 April 1506 3 December 1552), venerated as Saint Francis Xavier, was a Navarrese Catholic missionary and saint who was a co-founder of the Society of Jesus.

Born in Javier (Xavier in Old Spanish and in Navarro-Aragonese, or Xabier, a Basque word meaning "new house"), in the Kingdom of Navarre (in present-day Spain), he was a companion of Ignatius of Loyola and one of the first seven Jesuits who took vows of poverty and chastity at Montmartre, Paris in 1534. He led an extensive mission into Asia, mainly the Portuguese Empire in the East, and was influential in evangelisation work, most notably in early modern India. He was extensively involved in the missionary activity in Portuguese India. In 1546, Francis Xavier proposed the establishment of the Goan Inquisition in a letter addressed to the Portuguese King, John III.

While some sources claim that he actually asked for a special minister whose sole office would be to further Christianity in Goa, others disagree with this assertion. He was also the first Christian missionary to venture into Borneo, the Maluku Islands, and other areas. In those areas, struggling to learn the local languages and in the face of opposition, he had less success than what he had enjoyed in India. Xavier was about to extend his mission to Ming China, when he died on Shangchuan Island.

He was beatified by Pope Paul V on 25 October 1619 and canonized by Pope Gregory XV on 12 March 1622. In 1624, he was made co-patron of Navarre. Known as the "Apostle of the Indies", "Apostle of the Far East", "Apostle of China" and "Apostle of Japan", he is considered to be one of the greatest missionaries since Paul the Apostle. In 1927, Pope Pius XI published the decree "Apostolicorum in Missionibus" naming Francis Xavier, along with Thrse of Lisieux, co-patron of all foreign missions. He is now co-patron saint of Navarre, with Fermin. The Day of Navarre in Navarre, Spain, marks the anniversary of Francis Xavier's death, on 3 December 1552.

The Society of Jesus (Latin: Societas Iesu; abbreviated SJ), also known as the Jesuits (; Latin: Iesuitæ), 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 Gesù attached to the Church of the Gesù, 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.