The Oahu Interscholastic Association (OIA) is an athletic conference composed of all public secondary schools on the island of Oahu, Hawaii, U.S.A. The OIA was first founded in 1940 as the Rural Oahu Interscholastic Association (ROIA). The five founding schools were Castle High School, Kahuku High School, Leilehua High School, Waialua High & Intermediate School and Waipahu High School.