The California Interscholastic Federation-Southern Section (CIF-SS) is the governing body for high school athletics in most of Southern California and is the largest of the ten sections that comprise the California Interscholastic Federation (CIF). Its membership includes most public and private high schools in Orange, Los Angeles, Riverside, San Bernardino, Ventura, and central and southern Santa Barbara counties. Teams from the Los Angeles Unified School District (LAUSD) and surrounding areas have competed in the CIF Los Angeles City Section since 1935. CIF-SS's offices are located in Los Alamitos.

Founded in 1913, the CIF Southern Section includes over 560 member public and private high schools and is by far the largest CIF section. Three of the ten CIF sections are individual current or former public school districts (Los Angeles, San Francisco and Oakland). The Southern Section's membership includes all private schools located within the service area of the LAUSD, which includes almost all of the city of Los Angeles plus some adjacent areas outside the city limits. If the CIF Southern Section were a state association, it would be the 10th largest in the United States.

For its first year of operation, the organization was called the Southern California Interscholastic Athletic Council (SCIAC). That acronym was taken over by the Southern California Intercollegiate Athletic Conference in 1915 after the Southern Section name was established. CIF was officially formed in 1914 and became statewide in 1917. The service area was larger, encompassing what is now the CIF Los Angeles City Section, which broke off in 1935, and the CIF San Diego Section which broke off in 1960. Imperial County was once part of the section as well, but broke off in 2000 to join the San Diego Section. At various points in time, schools in Arizona, Nevada, and Tijuana, Baja California, Mexico, were part of the section.