inlet of the Gulf of Guinea, in western Gabon. It is fed by the Como and Mbeï rivers, which rise in the Cristal Mountains to the northeast. The estuary is 40 miles (64 km) long and 9 miles (14 km) wide at its mouth. It was explored in the 1470s by Portuguese navigators who may have named it Gabão (“Hooded Cloak with Sleeves”; hence Gabon) because of its shape, and it was long considered the finest harbour of the West African coast.

The main port on the estuary, Libreville, became Gabon's national capital and largest city. Logs are floated down the Como River to Owendo and Libreville on the estuary's northwest shore, and hydroelectric power is provided to the locality by a dam at Kinguélé upstream on the Mbeï River.