St. Mary's High School is a small, co-educational, college-preparatory Catholic high school located in downtown Annapolis, Maryland. It is part of the Roman Catholic Archdiocese of Baltimore. St. Mary's is accredited by AdvancED, the Archdiocese of Baltimore, and is recognized and approved by the Maryland State Department of Education.

Annapolis is the capital of the state of Maryland. It is the county seat of Anne Arundel County and its only incorporated city. Situated on the Chesapeake Bay at the mouth of the Severn River, 25 miles (40 km) south of Baltimore and about 30 miles (50 km) east of Washington, D.C., Annapolis forms part of the Baltimore–Washington metropolitan area. The 2020 census recorded its population as 40,812, an increase of 6.3% since 2010.