Africa is on the verge of a mining boom. We review the environmental threats from African mining development, including habitat alteration, infrastructure expansion, human migration, bushmeat hunting, corruption, and weak governance. We illustrate these threats in Central Africa, which contains the vast Congo rainforest, and show that more than a quarter of 4,151 recorded mineral occurrences are concentrated in three regions of biological endemism—the Cameroon-Gabon Lowlands, Eastern DRC Lowlands, and Albertine Rift Mountains—and that most of these sites are currently unprotected. Threats are not uniform spatially, and much of the Congo Basin is devoid of mineral occurrences and may be spared from direct mining impacts. Some of the environmental impacts of African mining development could potentially be offset: mining set-asides could protect some wildlife habitats, whereas improving transportation networks could increase crop yields and spare land for conservation. Research and policy measures are needed to (1) understand the synergies between mining and other development activities, (2) improve environmental impact assessments, (3) devise mitigation and offsetting mechanisms, and (4) identify market choke points where lobbying can improve environmental practice. Without careful management, rapid mining expansion and its associated secondary effects will have severe impacts on African environments and biodiversity.