The Cameroon line is a 1,000 km (620 mi) chain of volcanoes. It includes islands in the Gulf of Guinea and mountains that extend along the border region of eastern Nigeria and western Cameroon, from Mount Cameroon on the Gulf of Guinea north and east towards Lake Chad. The islands, which span the equator, have tropical climates and are home to many unique plant and bird species. The mainland mountain regions are much cooler than the surrounding lowlands, and also contain unique and ecologically important environments.

The Cameroon volcanic line is geologically unusual in extending through both the ocean and the continental crust. Various theories have been advanced by different geologists to explain the line.

In the Gulf of Guinea, the Cameroon line consists of six offshore volcanic swells that have formed islands or seamounts. From the southwest to the northeast the island groups are Pagalu (or Annobón), São Tomé, Príncipe and Bioko. Two large seamounts lie between São Tomé and Príncipe, and between Principe and Bioko. On the mainland, the line starts with Mount Cameroon and extends northeast in a range known as the Western High Plateau, home to the Cameroonian Highlands forests. Volcanic swells further inland are Manengouba, Bamboutu and the Oku Massif. East of Oku there are further volcanic mountains in the Ngaoundere Plateau, some of which appear to have similar origins.

Cameroon, officially the Republic of Cameroon (French: République du Cameroun), is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the Bight of Bonny, part of the Gulf of Guinea and the Atlantic Ocean. The country is called "Africa in miniature" for its geological and cultural diversity. Natural features include beaches, deserts, mountains, rainforests, and savannas. The highest point is Mount Cameroon in the southwest, and the largest cities are Douala, Yaoundé, and Garoua. Cameroon is home to over 200 different linguistic groups. The country is well known for its native styles of music, particularly makossa and bikutsi, and for its successful national football team. French and English are the official languages.

Early inhabitants of the territory included the Sao civilisation around Lake Chad and the Baka hunter-gatherers in the southeastern rainforest. Portuguese explorers reached the coast in the 15th century and named the area Rio dos Camarões ("River of Prawns"), the name from which Cameroon derives. Fulani soldiers founded the Adamawa Emirate in the north in the 19th century, and various ethnic groups of the west and northwest established powerful chiefdoms and fondoms. Cameroon became a German colony in 1884.