Calaveras Reservoir, Drinking water reservoir in Santa Clara County, California.

Calaveras Reservoir is a drinking water facility in Santa Clara County that collects water from Arroyo Hondo and Calaveras Creek. Water from this system is transported to surrounding areas for municipal use.

The original dam from 1913 failed structurally in 1918, leading to construction of a new facility in 1925. This new structure was at that time the largest earth-fill dam in the world.

The name Calaveras is Spanish for "skulls". Before the valley was flooded, it was farmland growing hay, strawberries and tomatoes; the farmers sold their land to the Spring Valley Water Company at the start of the 20th century so San Francisco could draw drinking water. The reservoir and dam are owned and run by the city and county of San Francisco.

Access to the reservoir is limited since the water is intended for drinking supply and water quality must be protected. Visitors should check which areas are publicly accessible and what restrictions apply.

A drought in 1991 led to the discovery of an airplane wreckage and two skeletons from a 1963 crash. This finding helped solve a decades-old case of missing persons.