The Kouilou-Niari River—also spelled Kwilu, Kwila, or Kwil—is the main drainage path for the coastal basin of the Republic of Congo. The river is called the Kouilou River along most of its length, but its center section, in the Niari region of The Congo, is called the Niari River. The river eventually combines with the Louessé River and eventually flows into the Atlantic Ocean. It covers about 450 miles from its origin in the plateaus of The Congo to its mouth at the coast.

The river has numerous waterfalls and is impassable from its mouth, which is blocked by multiple sandbars, formed primarily by the action of the Benguela current.

List of waterfalls

• Zrinski chutes: Honors Nikola Zrinski and Petar Zrinski , Croatian nobles; discovered and named in 1882 by a Croatian member (Dragutin Lerman) of Henry Morton Stanley's exploration team.