St. Ignatius College Preparatory
| Motto: Ad Majorem Dei Gloriam | |
| President | Father Anthony P. Sauer, S.J. |
| School type | Private |
| Religious affiliation | Jesuit |
| Founded | 1855 |
| Location | San Francisco, California |
| Enrollment | over 1,400 coed students |
| Faculty | 107 |
| Campus surroundings | Urban |
| Mascot | Wildcat |
Saint Ignatius College Preparatory or SI or "the Prep" is a preparatory school located in the Sunset District of San Francisco, California. It was founded in 1855 as an all-boys school by the Jesuits after the Gold Rush and is one of the oldest high schools in California. Though it still strongly maintains its Jesuit and Catholic identity, SI has since gone coed in 1989 and is home to 1,400 students. SI is celebrating the 150th anniversary of its founding in 2005.
Beginning as a one room schoolhouse run by Jesuit priests in the mid 19th century, SI has changed locations numerous times due to the growth of the student body and natural disasters. The fires following the 1906 earthquake destroyed the school's prime location on Market Street and forced the school to find a temporary location. In 1969, SI current campus opened its doors to students and has been education the youth of the Bay Area ever since.
Widely perceived as one of the top schools in California, SI has a history of academic excellence and accomplishments in other areas. It was ranked in the top 20 schools in America offering Advanced Placement classes - often used as an indicator of student achievement in college placement. It is also regarded as one of the most difficult schools for admission in Northern California.
SI excels in many other ways as well. Its facilities are among the best, including several athletic fields, tennis courts, a track, an indoor pool, a boathouse, etc. The Wildcats generally participate in the Western Catholic Athletic League (WCAL) in the Central Coast Section of California, though for some sports, teams belong to other leagues. Its athletics are highly ranked: the lacrosse team has consistently won the state championship and its men's rowing team recently ranked third in the nation. It has a wide range of extracurricular activities available for all its students. SI's famous rivalry with its cross-town rival, Sacred Heart Cathedral. The schools play each other in football, basketball, and baseball for the "Bruce-Mahoney" Trophy, which is named after two SI and SH alumni who died in World War II. The SI-SH rivalry is the oldest high school rivalry west of the Mississippi.
Over 96% of its graduating classes attend a 4-year institution, including many in the University of California system and the Ivy League. SI offers financial aid to applicants and is able make education affordable for many students with its sizable endowment. In 2004 the racial makeup of the student body was 63% White, 16% Asian, 6% Hispanic, 3% Black, and 12% mixed race.
Notable alumni include NFL Hall of Famer Dan Fouts and former California Gov. Jerry Brown.