Alkali Lake is a geographic sink located in Lake County, Oregon, United States. It lies within the Alkali Subbasin of the Summer Lake Basin watershed in southeastern Oregon. The lake is situated 26 miles east of Christmas Valley, Oregon, northeast of Lake Abert, and directly west of Abert Rim and Highway 395.
Alkali Lake is believed to have reached a prehistoric maximum depth of 270.7 feet (82.5 meters) and covered about 1,448.4 square miles (3,751 square kilometers). Since then, its water level has fluctuated, with a general trend towards drying. Notable features include dissolved alkaline salts averaging 10% of total brine weight in its seasonal waters and a nearby chemical disaster, Alkali Lake Chemical Waste Dump.