Maputo Bay, formerly Delagoa Bay (dĕl´əgō´ə), inlet of the Indian Ocean, c.55 mi (90 km) long and 20 mi (30 km) wide, S Mozambique, SE Africa; Maputo, the capital and chief port of Mozambique, is on the bay. Maputo Bay is a large deepwater harbor, with numerous quays to handle oceangoing vessels; railroads lead into the interior. The first Westerner to visit (1502) the bay was António do Campo, one of Vasco da Gama's captains; the area was explored in 1544 by Lourenço Marques, the Portuguese trader. In the 1700s, Dutch and Austrian trading companies tried to establish posts on the bay; both were driven out by malaria and the Portuguese. In 1787, Portugal built a fort there, around which the town of Lourenço Marques (Maputo) grew. In the mid-1800s, Portugal's claim to the area was challenged by Great Britain and by the Transvaal when it was realized that the bay provided a major access route to the Kimberley diamond mines. The Transvaal recognized Portugal's sovereignty in 1869, and in 1875 France, acting as arbiter, awarded the area to Portugal.