main tributary of the Kasai River (itself a tributary of the Congo River) in Congo (Kinshasa), central Africa. About 750 miles (1,200 km) long, it begins in the western highlands of Katanga (Shaba), where it is known as the Lubilash River, and flows 285 miles (460 km) north and northwest, where it becomes the Sankuru proper and where it flows northward and then almost directly westward to the Kasai. The Sankuru is navigable for 365 miles (590 km) below the town of Pamia-Mutombo, north of the city of Mbuji-Mayi.