St. Francis de Sales Church is a Roman Catholic Oratory located in south St. Louis, Missouri, United States. It is the second largest church in the Archdiocese of St. Louis after the cathedral-basilica. The church is popularly known as the "Cathedral of South St. Louis".

The Institute of Christ the King Sovereign Priest, Latin: Institutum Christi Regis Summi Sacerdotis, abbreviated as ICRSS and ICKSP, is a society of apostolic life of pontifical right in communion with the Holy See of the Catholic Church. The institute has the stated goal of honouring God and the sanctification of priests in the service of the Catholic Church and souls. An integral part of the institute's charism is the use of the traditional liturgy, namely the Tridentine Missal for Mass, the Breviary of John XXIII for the Divine Office, and the Rituale Romanum for other sacraments. The society has undertaken the restoration of a number of historic church buildings.