(Portug. Ilha do Principe), an island of Africa, belonging to Portugal, in the Bight of Biafra, 140 miles S.S.W. of Fernando Po; length from N. to S., 10 miles; breadth, about 5 miles. It is mountainous and of volcanic origin, the summits of some of the hills rising to the height of 4000 feet. The soil is in general hard and stony, but in some places it is of great fertility. It is watered by many springs and streams. Timber for various uses, and dye-woods, are obtained here in abundance. Much of the island is occupied by plantations of coffee, which is the principal produce, and of which 3487 cwt. were exported in 1842. The atmosphere is extremely moist; and, except for a few months, showers prevail during the whole year. The trade of the island, which was once considerable, has for some time been in a declining condition. St Antao, on the N.E. coast, is the chief town. Pop. of the island, 4584, chiefly slaves.