Lake Elsinore, Natural freshwater lake in Southern California, US

Lake Elsinore is the largest natural freshwater lake in Southern California, covering 12.1 km² (about 3,000 acres) at an elevation of 379 m. It measures 9.7 km long and 2.4 km wide, with a maximum depth of 13 m. Fed by the San Jacinto River, it lies in a basin bordered by the Elsinore Mountains to the west and southwest.

The Luiseño people originally inhabited the valley and left rock paintings and artifacts throughout the region. The lake later became a destination for recreational activities during the 1900s.

The lake's name comes from the town of Elsinore, founded on its northeastern shore on April 9, 1888; Spanish explorers had called the water Laguna Grande. The Lake Shore Beach Club, an African American resort, once stood on its shores. Visitors today still camp and water animals along the southern shore, the route of the old Southern Emigrant Trail and Butterfield Overland Mail.

Multiple access points around the lake allow for boating, fishing, and water sports like jet skiing and paddleboarding. The best time to visit is during cooler months when crowds are smaller and the sun is less intense.

The lake is the terminal basin of a partially closed watershed of 750 square miles, lying at its lowest point at 379 metres above sea level. When the water reaches 383 metres it spills into Temescal Wash, which runs northwest through Temescal Canyon to Alberhill Creek and on to the Santa Ana River.