Boma, city and port on the Congo River estuary, southwestern Democratic Republic of the Congo. It lies 60 miles (100 km) from the Atlantic Ocean. One of the nation’s oldest communities, it was a trading centre and slave market before the middle of the 19th century. In 1886 Boma became the capital of the Congo Free State, later the Belgian Congo, until replaced by Léopoldville (now Kinshasa) in 1926. Boma is the terminus of a railroad to Tshela and is the outlet for palm oil, bananas, and timber from the forest area of Mayumbe to the north. Pop. (2004 est.) 171,552.