The Ubangi River, also spelled Oubangui, is the largest right-bank tributary of the Congo River in the region of Central Africa. It begins at the confluence of the Mbomou and Uele Rivers and flows west, forming the border between Central African Republic (CAR) and Democratic Republic of the Congo. Subsequently, the Ubangi bends to the southwest and passes through Bangui, the capital of the CAR, after which it flows south – forming the border between Democratic Republic of the Congo and Republic of the Congo. The Ubangi finally joins the Congo River at Liranga.

The Congo River, formerly also known as the Zaire River, is the second-longest river in Africa, shorter only than the Nile, as well as the third-largest river in the world by discharge volume, following the Amazon and Ganges rivers. It is the world's deepest recorded river, with measured depths of around 220 m (720 ft). The Congo–Lualaba–Luvua–Luapula–Chambeshi River system has an overall length of 4,700 km (2,900 mi), which makes it the world's ninth-longest river. The Chambeshi is a tributary of the Lualaba River, and Lualaba is the name of the Congo River upstream of Boyoma Falls, extending for 1,800 km (1,100 mi).