Trinity Catholic High School was a private, Catholic high school in Spanish Lake Township, St. Louis County, Missouri. It was located in the Archdiocese of Saint Louis. The school closed in 2021.

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.