Mammoth Pool Dam, Embankment dam and hydroelectric station in Sierra National Forest, California.

Mammoth Pool Dam is a rock-filled embankment that spans across the San Joaquin River in the Sierra National Forest, creating a large reservoir at a height of about 125 meters. The structure functions as both a water storage facility and a power generation station.

Southern California Edison completed the dam in 1959 after redirecting the San Joaquin River through a tunnel to support the construction. This project marked a major development in hydroelectric infrastructure for the region.

The name comes from a large natural pool that once lay in the San Joaquin River above the present dam site. The Mammoth Pool site itself was chosen because the canyon narrows to a gap between walls of solid granite. The reservoir is closed to all public use from May 15 to June 15 so mule deer can migrate undisturbed.

The area around the reservoir offers swimming, fishing, and boating opportunities, though access may be restricted at certain times of year. Plan ahead and check conditions before visiting, as the location in the mountains requires some travel preparation.

The 1,004 ft (306 m) head of water feeding the powerhouse is almost three times the dam's own structural height of 411 ft (125 m). The reservoir's name recalls a large natural pool in the San Joaquin River that once lay above the present dam site.