Saint Mary's High School (SMHS), founded in 1876, is a Roman Catholic, co-educational, college preparatory school in Stockton, California. The school is under the canonical jurisdiction of the Diocese of Stockton and sponsored by the Salesian order of the Oblates of St. Francis de Sales priests and brothers. The school is a member of the College Board and is accredited by the Western Association of Schools and Colleges and by the Western Catholic Education Association.

Stockton is a city in and the county seat of San Joaquin County in the Central Valley of the U.S. state of California. Stockton is the most populous city in the county, the 11th-most populous city in California and the 58th-most populous city in the United States. Stockton's population in 2020 was 320,804. It was named an All-America City in 1999, 2004, 2015, and again in 2017 and 2018. The city is located on the San Joaquin River in the northern San Joaquin Valley. It lies at the southeastern corner of a large inland river delta that isolates it from other nearby cities such as Sacramento and those of the San Francisco Bay Area.