Bornu, former Muslim state, mostly in NE Nigeria, extending S and W of Lake Chad. It began its existence as a separate state in the late 14th cent. From the 14th to the 18th cent. Bornu exported slaves, eunuchs, fabrics dyed with saffron, and other goods to N Africa. Bornu reached its peak under the mai (ruler) Idris Alawma (ruled 1570-1610), when it was the leading state in the central Sudan region. Bornu declined from the 17th cent. In the early 19th cent. it was severely threatened by the Fulani but maintained its independence when Muhammad al-Kanemi (ruled 1814-35), who established a new dynasty, revived the state. However, Bornu began to decline again after c.1850 because of weak rulers, and was conquered (1893-96) by the forces of Rabih, a Sudanese slave trader. In 1898, Bornu was divided among Great Britain, France, and Germany. In 1922 the German portion became part of the British Cameroons mandate of the League of Nations.

Former African empire around Lake Chad. It was ruled by the Sef dynasty in the 9th–19th century. Its territory at various times included what is now southern Chad, northern Cameroon, northeastern Nigeria, eastern Niger, and southern Libya. Probably founded in the mid-9th century, it became an Islamic state at the end of the 11th century. Its location made it a trading hub between North Africa, the Nile Valley, and the sub-Saharan region. From the 16th century Kanem-Bornu, sometimes called simply Bornu, was extended and consolidated. The Sef dynasty died out in 1846.

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Historical region, northeastern Nigeria. Prominent physical features include a vast plain, a volcanic plateau, and swamps south of Lake Chad. Now inhabited chiefly by the Kanuri people, it constituted a Muslim kingdom from about the 11th century. Together with Kanem it later formed an empire (see Kanem-Bornu), which reached the height of its power circa 1570–1600. In 1902 it became part of Nigeria, which was then under British rule. The region is largely contained in Nigeria's present-day state of Borno.

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Bornu may refer to:

• Bornu Empire, a historical state of West Africa
• Borno State, Nigeria