Lower Klamath Lake is a lake in Siskiyou County, California. At one time it was connected to Upper Klamath Lake. It currently is used to hold overflow water for Klamath Project irrigation uses.

Lower Klamath Lake
Freshwater marsh on Lower Klamath Lake
Lower Klamath Lake Show map of California Lower Klamath Lake Show map of the United States
Location	Siskiyou County, California
Coordinates	41°59′27″N 121°44′35″W / 41.9908483°N 121.7431633°W / 41.9908483; -121.7431633[1]
Basin countries	United States

The lake is in Northern California, near the border with Oregon. The Lower Klamath National Wildlife Refuge (est. 1908), which covers the northern part of the lake, extends from California into Oregon.

The area around the lake was in the homeland of the indigenous Modoc people, prior to mid−19th century Anglo−American immigration.