The Conference of Independent Schools of Ontario Athletic Association, or CISAA, is a sports conference for various private schools located primarily in the southern part of the province of Ontario. Many of the institutions are located in or near the Greater Toronto Area; One member school, Nichols School, is located in Buffalo, New York.
The CISAA grew out of the Little Big Four conference, consisting of Upper Canada College, Toronto; St. Andrew's College, Aurora; Ridley College, St. Catharines; and Trinity College School (TCS), Port Hope; four of the oldest private schools in Canada. Teams for the 37 schools currently in the CISAA regularly compete in numerous sports against public high schools in the Ontario Federation of Schools Athletic Association (OFSAA) provincial championships.