The Cavalla River (also known as the Cavally, the Youbou and the Diougou) is a river in West Africa running from north of Mont Nimba in Guinea, through Côte d'Ivoire, to Zwedru in Liberia, and back to the border with Côte d'Ivoire. It ends in the Gulf of Guinea 21 km (13 mi) east of Harper, Liberia.