The Archdiocese of St. Louis is a Latin Church ecclesiastical territory or archdiocese of the Catholic Church that covers the City of St. Louis and the Missouri counties of Franklin, Jefferson, Lincoln, Perry, Saint Charles, Saint Francois, Ste. Genevieve, St. Louis, Warren, and Washington. It is the metropolitan see of the ecclesiastical province containing three suffragan sees: Diocese of Springfield-Cape Girardeau, the Diocese of Jefferson City, and the Diocese of Kansas City-Saint Joseph. It is led by Archbishop, Mitchell Thomas Rozanski, formerly the Bishop of Springfield in Massachusetts.

The Diocese of Springfield–Cape Girardeau is a Latin Church ecclesiastical territory, or diocese, of the Catholic Church in southern Missouri in the United States. It is a suffragan diocese in the ecclesiastical province of the metropolitan Archdiocese of Saint Louis.