The 2025 Orange County (OC) Fair in Costa Mesa, California, runs from July 18 through August 17, 2025. The fair is open Wednesday, Thursday, and Sunday from 11 a.m. to 11 p.m., and Friday and Saturday from 11 a.m. to midnight. It is closed on Mondays and Tuesdays. Tickets must be purchased in advance, as there is limited daily capacity and no tickets are sold at the gate during the event.