Upper Klamath Lake (sometimes called Klamath Lake) (Klamath: ?ews, "lake" ) is a large, shallow freshwater lake east of the Cascade Range in south-central Oregon in the United States. The largest body of fresh water by surface area in Oregon, it is approximately 25 miles (40 km) long and 8 miles (13 km) wide and extends northwest from the city of Klamath Falls.