The Republic of Guinea, also referred to as Guinea-Conakry to distinguish it from its neighbour Guinea-Bissau, is located on the North Atlantic Coast of West Africa. It shares its northern border with Guinea-Bissau, Senegal, and Mali and its southern border with Sierra Leone, Liberia, and Côte d'Ivoire (Ivory Coast). The country covers a total of 245,857 km2 and is divided into four geographic regions: the coastal lowlands (Lower Guinea), which is part of the Guinean forest-savanna mosaic ecoregion; the pastoral Fouta Djallon highlands (Middle Guinea); the northern savanna (Upper Guinea); and a southeastern rain-forest region (Forest Guinea). The Niger, Gambia, and Senegal Rivers are among the 22 West African rivers that have their origins in Guinea’s mountains. The highest point in Guinea is Mont Nimba at 1,752 m, part of the Nimba massif that sits astride the borders with the Côte d'Ivoire and Liberia.


Major parts of Guinea are underlain by crystalline basement Precambrian rocks comprising gneiss, migmatites and granitic intrusions that correspond to the southern portion of the West African Craton. The eastern two-thirds of the country is dominated by schists of the Kenema-Man domain and the Paleoproterozoic Birrimian System. Neoproterozoic and Paleozoic sediments with a basal tillite and overlying sandstones, marls and quartzites form wide parts of northern Guinea. Along the coast there occurs a strip of Neogene marine and alluvial sediments. A major N-S line of kimberlite dykes and pipes is present in southern Guinea.