Whale Rock Reservoir, Reservoir near Cayucos, San Luis Obispo County, California, United States

Whale Rock Reservoir is a large body of water in California managed by the local water department to supply the community. The reservoir sits in a hilly landscape surrounded by open grassland with scattered trees and few nearby structures.

Whale Rock Dam, a 193-foot earthfill structure on Old Creek, was completed in 1961 by the Whale Rock Commission. The resulting reservoir holds 40,662 acre-feet and supplies drinking water to San Luis Obispo, the California Men's Colony, Cal Poly, and the Cayucos Area Water Organization via the 17.6-mile Whale Rock Conduit.

The reservoir is not open for swimming or boating and is primarily used for water storage. Visitors can walk on open land around it, but should stay on designated paths and avoid disturbing wildlife.

The reservoir is filled by Old Creek, whose watershed covers 20.6 square miles (53 km2). Drinking water reaches San Luis Obispo through the Whale Rock Conduit, a 17.6-mile (28.3 km) pipeline with a 30-inch (760 mm) diameter.