Clear Lake Reservoir is a reservoir in the Klamath Basin and the Modoc National Forest, in northwestern Modoc County, California.
It is part of the Klamath Project. and about 40mi northwest of Alturas. It is formed by Clear Lake Dam on the Lost River, a tributary of the Klamath River, and has a capacity of 527,000acre.ft. The reservoir is not to be confused with Clear Lake, a large natural lake on Cache Creek in Lake County, California.