The Firehole River is one of two major tributaries of the Madison River. It flows north approximately 21 miles (34 km) from its source in Madison Lake on the Continental Divide to join the Gibbon River at Madison Junction in Yellowstone National Park. The Firehole flows through several significant geyser basins in the park to include the Upper Geyser Basin, which contains the world-famous geyser Old Faithful. The river was named by early trappers for the steam that makes it appear to be smoking as if on fire.
The Firehole contains three of Yellowstone's major waterfalls: Kepler Cascades south of Old Faithful, Firehole Falls and the Cascades of the Firehole in Firehole Canyon.