The Kentucky River is a tributary of the Ohio River, 260 miles (418 km) long, in the U.S. Commonwealth of Kentucky. The river and its tributaries drain much of the central region of the state, with its upper course passing through the coal-mining regions of the Cumberland Mountains, and its lower course passing through the Bluegrass region in the north central part of the state. Its watershed encompasses about 7,000 square miles (18,000 km2). It supplies drinking water to about one-sixth of the population of the Commonwealth of Kentucky.