The majority of modern lateritic bauxite deposits are found in a small number of provinces located in the present-day tropical and subtropical belts. Ancient bauxites formed under similar climatic conditions are located at higher latitudes. Bauxites form in hot, humid climates with pronounced wet and dry seasons in well-drained environments. Under similar but drier conditions, ferruginous lateritic regoliths form instead. Where climates change to very wet, rainforest conditions, such as in Amazonia, bauxites are replaced by clay materials. Surface zones are overburdened sedimentary clays and, with depth, metasomatic kaolinite, then bauxites. The weathering processes that result in the formation of bauxitic lateritic regoliths are typically the result of acid leaching by infiltration of rainwater, which has a pH of 5.0–5.5, mainly due to dissolved atmospheric CO2. A Transition zone at the base of the bauxite horizon is controlled by seasonal fluctuations of the groundwater level due to the direct penetration of water from the surface by open fissures during the wet season. Bedrock composition and geomorphology are critical controls in the formation of bauxite deposits. In order to form bauxites, bedrock should be enriched in alumina, have good filtration coefficients, and ideally have sub-horizontal bedding for stratal formations. The distribution and quality of bauxites are influenced by geomorphological factors. Many of the examples are drawn from the Fouta Djallon Bauxite sub-province, Guinea.