This article describes ironmaking and steelmaking practices (melt or liquid processing, including hot metal desulfurization) and discusses the evolution of these processes and their effects on steel properties. The physical chemistry of steelmaking may appear deceptively simple for integrated steel mill operations where ore from the ground is converted into steel. The various refining steps that occur in steelmaking are reviewed. The article also describes solid processing of steel, with emphasis on hot and cold rolling, thermomechanical processing, and annealing of flat steel products.