Tenkiller Ferry Lake, or more simply, Lake Tenkiller, is a reservoir in eastern Oklahoma formed by the damming of the Illinois River. The earth-fill dam was constructed between 1947 and 1952 by the United States Army Corps of Engineers for purposes of flood control, hydroelectric power generation, water supply and recreation. It went into full operation in 1953. The lake and dam were named for the Tenkiller family, prominent Cherokees who owned the land and ferry that were bought for the project. This is the 6th largest lake in Oklahoma, based on water capacity.

The Illinois River is a 145-mile-long (233 km) tributary of the Arkansas River in the U.S. states of Arkansas and Oklahoma. The Osage Indians named it Ne-eng-wah-kon-dah, which translates as "Medicine Stone River". The state of Oklahoma has designated its portion as a Scenic River.