This article describes the Bayer process for the purification of alumina. The process includes four major stages: digestion, clarification, precipitation, and calcination. The article discusses the aluminum electrolytic process in terms of aluminum electrolysis cell design, magnetohydrodynamic forces, and cathode lining. It reviews the electrochemical reactions and thermodynamics for aluminum electrolysis. The article also describes the cell operations and cell stability, as well as the key indicators of cell performance. It schematically illustrates the typical costs producing aluminum in an aluminum smelter. The article also discusses various environmental issues, such as fluoride recovery; perfluorocarbons, polycyclic aromatic hydrocarbons, and sulfur emissions; spent pot lining; and development of inert anodes and CO2 emissions.