The Ubangi River (also Oubangi) is a major tributary of the Congo River in central Africa. It is considered to begin at the junction of the Mbomou and Uele Rivers, flows west for about 350 km, then bends to the southwest, passes through Bangui, then flows south for another 500 km to the Congo.

From its start to 100 km below Bangui, the Ubangi defines the boundary between the Central African Republic and the Democratic Republic of the Congo (DRC). Thereafter, it forms the boundary between the DRC and the Republic of Congo until it empties into the Congo River.