The book is a production and technical monograph that sets out the foundations of the theory of the water electrolysis process and the most important principles for the design of electrolyzers for the production of hydrogen and oxygen. The most common designs of modern electrolyzers operating at atmospheric pressure and elevated pressure are described; their main technical indicators, methods of material and thermal calculation of electrolyzers are given; automation of monitoring and control of water electrolysis process, as well as corrosion of electrolyzer parts are considered.