Cathedral Catholic High School (CCHS) is a private coeducational Catholic college preparatory day school in San Diego, California serving grades 9–12. It is operated by the Diocese of San Diego. In 1970, Cathedral Girls High School, a girls’ school dating back to 1939 and located in downtown San Diego, merged with the all-boys University High School founded in 1957. In 1971, the newly constituted and expanded University of San Diego High School graduated its first coeducational class. Uni or the University of San Diego High School (USDHS), was located in the Linda Vista neighborhood of San Diego. Construction began on CCHS at its current location on Del Mar Heights Road in Carmel Valley in 1999. In 2005, the school including all faculty, administration, and students, moved to that campus and changed its name to Cathedral Catholic High School. Cathedral Catholic High School is accredited by the Western Catholic Education Association (WCEA), the Western Association of Schools and Colleges (WASC) and holds membership with the College Board.

The Diocese of San Diego is a Latin Church ecclesiastical territory or diocese of the Catholic Church in Southern California, United States. Its ecclesiastical territory includes all of San Diego and Imperial Counties.