Tule Lake, Intermittent lake in Siskiyou and Modoc Counties, California, US

Tule Lake is an intermittent lake of 13,000 acres (20 sq mi) in northeastern Siskiyou County and northwestern Modoc County, California, on the Oregon border. It measures about five miles long and three miles across, fed by the Lost River, and lies at 4,035 feet (1,230 m) above sea level, 1.5 miles southwest of the town of Tulelake.

The area saw conflicts between the Modoc people and US forces in the 1870s, including a significant confrontation involving General Edward Canby. During World War II, a large detention center operated nearby to hold Japanese Americans and became one of the most crowded facilities of its kind.

The lake lies within the Tule Lake National Wildlife Refuge, and water deliveries from the Klamath Project keep it wet enough for wildlife; on 24 July 2020 such a delivery saved 50,000 ducklings. The name comes from the tule reeds that grow in its marshes. Canby's Cross, about 3 miles south, marks where Modoc chief Kintpuash killed General Edward Canby.

Tule Lake lies 2.4 km southwest of the town of Tulelake, within the Tule Lake National Wildlife Refuge and the Klamath Project. Water deliveries from the project keep the refuge supplied for wildlife, so the lake extent shifts with drought and irrigation. Check current water levels before planning a visit.

This body of water is one of fewer than twenty lakes on Earth known to have existed continuously for over one million years. This extreme age makes it a geologically significant location for understanding long-term ecosystem stability.