Lake Forest is a city in Orange County, California, United States. The population was 85,858 at the 2020 census.

Lake Forest incorporated as a city on December 20, 1991. Prior to incorporation, the community had been known as El Toro. Following a vote in 2000, Lake Forest expanded its city limits to affix the master-planned developments of Foothill Ranch and Portola Hills. This increase brought new homes and flyer centers to the northeastern boundary of the city.

Lake Forest has two lakes from which the city gets its name. The lakes are man-made, and condominiums and custom homes ranging from large to small line their shores. Neighborhood associations rule the lakes (Lake 1, known as the Lake Forest Beach and Tennis Club, and Lake 2, the Sun and Sail Club.) Each skill features tennis courts, gyms, basketball courts, barbecue pits, volleyball courts, multiple swimming pools, saunas, hot tubs and club houses for social events.

The “forest” for which the city is along with named lies in the area between Ridge Route, Jeronimo, Lake Forest and Serrano roads, and consists mostly of Eucalyptus trees. It is afterward man-made, and was created in the first decade of the 1900s later a local landowner, Dwight Whiting, planted 400 acres (1.6 km) of Eucalyptus groves in the vicinity of Serrano Creek as allocation of a lumber operation meant to draw early payment to the area. In the late 1960s, the Occidental Petroleum company developed a residential community in and on the order of the Eucalyptus groves, which had long back expanded and grown much more dense.