Lake San Antonio, Reservoir in Monterey County, California, US.

Lake San Antonio is a reservoir formed by San Antonio Dam on the San Antonio River, lying mostly in southern Monterey County with part in northern San Luis Obispo County. The 202-foot dam, completed in 1965, holds up to 350,000 acre-feet. The south shore has 26 miles of trails.

The lake was created by the San Antonio Dam, completed in 1965. This construction project was a major undertaking that shaped the region and established the water body that exists today.

The lake hosts a major triathlon event each year that draws athletes from around the world. Visitors can feel the energy of this sporting gathering and the community spirit that forms around the water during the competition.

Over 500 campsites line both the north and south shores, many with RV hookups, plus more in forested areas a short walk from the water. The North Shore allows shoreline camping at the water's edge, so boaters can keep vessels moored by their site. Water levels have swung widely since 2013, sometimes leaving boat ramps unusable.

Bald eagles winter at the lake, and Monterey County Parks runs viewing tours in January and February that must be reserved in advance, often selling out weeks ahead. The lake is also one of the few in California where shoreline camping is allowed at the water's edge on the North Shore.