Mater Dei High School is a private, Catholic, co-educational secondary school in Santa Ana, California, located in and administered by the Diocese of Orange.

Santa Ana is a city in and the county seat of Orange County, California, United States. Located in the Greater Los Angeles region of Southern California, the city's population was 310,227 at the 2020 census, making Santa Ana the second most populous city in Orange County, the 13th-most populous city in California, and the 64th densest large city in the United States. Santa Ana is a major regional economic and cultural hub for the Orange Coast.