Tolay Lake is a shallow freshwater lake in southern Sonoma County, California, United States. The lake, nestled within the southern vestiges of the Sonoma Mountains, is the site of significant Native American prehistoric seasonal settlement. In 2005, Sonoma County acquired the entirety of the lake and virtually its whole drainage basin from the Cardoza family for the sum of $18 million; the county's intention is to utilize the property as Tolay Lake Regional Park for ecological and archaeological preservation, as well as public use and enjoyment. Tolay Lake and its immediate drainage area is home to several nesting pairs of golden eagles, Aquila chrysaetos, and a number of rare, threatened or endangered species including the California red-legged frog, Rana draytonii; Western pond turtle, Actinemys marmorata; and Western burrowing owl, Athene cunicularia.

Sonoma County is located in the U.S. state of California. As of the 2020 United States Census, its population was 488,863. Its seat of government and largest city is Santa Rosa.