Summer Lake is a large, shallow, alkali lake in Lake County, Oregon, United States located 5 miles (8 km) south of the small, unincorporated community of Summer Lake, Oregon. At high water it is about 15 miles (24 km) long and 5 miles (8 km) wide, and supports a wide variety of birds and other wildlife in its marshes. The lake was named by explorer John C. Frémont on his expedition into Central Oregon in 1843.

A soda lake or alkaline lake is a lake on the strongly alkaline side of neutrality, typically with a pH value between 9 and 12. They are characterized by high concentrations of carbonate salts, typically sodium carbonate, giving rise to their alkalinity. In addition, many soda lakes also contain high concentrations of sodium chloride and other dissolved salts, making them saline or hypersaline lakes as well. High pH and salinity often coincide, because of how soda lakes develop. The resulting hypersaline and highly alkalic soda lakes are considered some of the most extreme aquatic environments on Earth.