This review is devoted to membrane electrolysis, in particular utilizing ion-selective membranes, as an important part of both existing and emerging industrial electrochemical processes. It aims to provide fundamental information on the history and development, current status and future perspectives of membrane electrolysis. An overview of the history of electromembrane processes is given with the focus on brine electrolysis since it is the predominant electrochemical industrial technology utilizing ion-selective membranes. This is followed by a summary of the wide range of hydrogen-based energy conversion processes with different degrees of maturity, i.e. water electrolysis and fuel cells, which promise to become the next generation of major electromembrane processes. The overview of the state-of-the-art is rounded off by a number of smaller-scale processes utilizing ionically conducting solid electrolytes and ion-selective membranes that are already commercially available. The article concludes by considering potential future developments in this exciting field of electrochemistry.