Santi Celso e Giuliano is a minor basilica[1] and papal chapel of the Diocese of Rome in the care of the Institute of Christ the King Sovereign Priest.

[3] Canons of the collegiate church are mentioned in the fourteenth century[4] and at around the same time it served as the chapel for the procurators of the Audientia,[5] a predecessor body to the Apostolic Signatura.

[7] It was also during this time that the church became tied to the Office of Ceremonies, (the predecessor body to the Sacred Congregation of Rites), primarily through the work of Paris de Grassis.

[7] This connection was strengthened by the church's placement at the start of the strada papale, the processional route a newly elected Pope followed to take possession of St. John Lateran.

[7] In 1518, Biagio da Cesena, Papal Master of Ceremonies to Pope Leo X, Adrian VI, Clement VII and Paul III,[9] was appointed archpriest of the church.