The Congo River Tributary is a major river in Central Africa. It is the second largest river in Africa and the ninth longest in the world. Two of its tributaries are the Ubangi (6 letters) and the Ebola (5 letters). The Ubangi is the largest tributary of the Congo River, originating in the Central African Republic and flowing through the Democratic Republic of the Congo. The Ebola is a smaller tributary of the Congo River, originating in the Democratic Republic of the Congo and flowing into the Ubangi.