Eagle Lake is a lake at 5,098 ft (1,554 m) elevation in Lassen County approximately 15 miles north of Susanville, California. It is the second largest natural lake entirely in the state of California, United States. Eagle Lake is home to Osprey (Pandion haliaetus) and Bald Eagles (Haliaeetus leucocephalus), from which it gets its name.
Eagle Lake is the only watershed which supports Eagle Lake trout (Oncorhynchus mykiss aquilarum). These Rainbow trout grow to very large sizes, possibly having evolved to live longer as low flows often restrict spawning runs up their main spawning stream, Pine Creek. The average size of Eagle Lake trout are about 1½ pounds and can exceed 10 pounds. Adults quickly grow to a size of 17 to 18 inches in three years and can live for up to 11 years. Since these Modoc Lakes are high in alkalinity, the trout have evolved to only be able to live in these lakes. These trout were once so abundant that there was a commercial fishery for them in the late 19th century.