Lake Mission Viejo, Recreational lake in Mission Viejo, California, US

Lake Mission Viejo is a reservoir formed by an earthfill dam across the canyon of Oso Creek, about 5 miles south of Santiago Peak. It covers approximately 124 surface acres of water and 50 acres of land, including two main beaches, Playa del Norte and Playa del Este, and a marina in the northwestern arm.

Lake Mission Viejo was built as a recreational reservoir in Mission Viejo, formed by an earthfill dam across the canyon of Oso Creek, part of the Trabuco Creek and San Juan Creek drainage basin. Construction was initially estimated to cost around $10 million. The lake is not fed by urban runoff and is maintained to be safe for contact.

Lake Mission Viejo is a private facility for members of the Lake Mission Viejo Association, the homeowners within the planned community. Summer brings concerts, movie nights and summer camps, and the Annual Jazz Fest and Taste of the Lake is held at North Beach, whose snack bar serves a special menu on concert days.

Access to the lake is through guard gates at North Beach and East Beach, and the facilities are reserved for Lake Association members and their guests. North Beach stays open all year and holds the administration buildings, boat rentals and boat launching; East Beach opens daily in summer and on weekends from Memorial Day through Labor Day. Members may fish from the shoreline area next to the marina or from a boat, and only specified baits are allowed.

The lake maintains notably clean water by preventing urban runoff and using regular testing systems to monitor aquatic conditions. This approach keeps the water quality higher than typical urban water bodies.