Congo, the great equatorial river of Central Africa, in respect of its basin the second largest river of the world, has its reservoir in Lake Bangweolo, of which the Chambezi is the largest feeder, and into which also flow numerous streams from the Lokinga Mountains on the south. From Bangweolo the great river issues under the name of the Luapula; and flowing in a northerly direction, it expands into Lake Moero, on leaving which it is called, as far as Nyangwe, the Lualaba. From Nyangwe to Stanley Falls, Stanley christened it the Livingstone; and from Stanley Falls to the mouth it is known by the name of the Congo.

Its length has been calculated variously at a little under and a little over 3000 miles; it drains an area of more than 1,300,000 sq. m,; and it discharges a body of water into the ocean second only to the Amazon. Such is the power and force of this mighty stream that no delta exists at its mouth. Vessels take in fresh water at its entrance into the sea. The two largest tributaries of the Congo are the Kassai from the south, explored (1885) by Wissmann; and the Mobangi, from the north, explored (1884-85) by Grenfell, and afterwards by Vangele. Other tributaries are the Kwa or Kwango, the Juapa and Bosira, the Ikelemba, the Lulongo, and the Lumami rivers on the south or left bank; and the Aruwimi, the Mbura, the Loika, the Ngala, the Lokinga Nkundji, etc, on the north or right bank. As regards commerce and navigation, the Congo may be divided into three parts - Lower, Middle, and Upper. The lower region extends from Banana at the mouth to the foot of the first rapids, 110 miles, navigable by ocean steamers drawing 18 feet. The middle or cataract region extends from Vivi to Stanley Pool, 235 miles, navigable for 70 miles by small steamers or iron whaleboats; and a railway, surveyed in 1888, from Vivi to Leopoldville (250 miles), was soon thereafter begun, keeping mostly at a distance of about 30 miles south of the river. The mortality of the workers employed in the construction of the railway was very high, and labourers had to be imported from Dahomey and the Gold Coast regions. Chinese coolies were also employed. The first 25 miles were open for traffic in 1893, and the railway from Matadi to Leopoldville was completed by 1S98. The upper region of the river from Stanley Pool to Stanley Falls, 1068 miles, is navigable for steamers with a draught of four feet, besides over 3000 miles of navigable tributaries.

The river, whose mouth was discovered in 1484-85 by Diego Cam, was known to the Portuguese as the Zaire, a corruption of the native words Nzari, Nyali, or Niadi, meaning 'river; ' while the country about it and south of it was known as Congo. The centre of Portuguese missions was San Salvador. In 1818 Captain Tuckey was sent by the British government, and explored 118 miles of the river. In 1867-71 Livingstone discovered the Luapula and Lualaba, which he supposed to be the head-waters of the Nile; but which in 1876-77 Stanley proved, by following it down, to be really the Congo.