PEM Water Electrolysis: Fundamentals and Practice is a comprehensive reference on the design and operation of PEM water electrolyzers. Combining hydrogen production with engineering thermophysics, the book provides a unique resource for understanding the hydrogen production process, from fundamental concepts to practical implementation. Divided into four parts, the book covers the current state of hydrogen and the fundamentals of PEM water electrolysis and the various components and materials used in PEM electrolysis, including electrocatalysts, proton exchange membranes, membrane electrode assembly, porous transport layer, flow field, and corrosion, and more. Other sections explain the key processes involved in PEM electrolysis, such as two-phase flow, heat and mass transfer and delve into systems research, covering grid fluctuations, control systems, assembly, diagnosis, and commercialization. In addition, the book provides comprehensive information on the modeling of PEM electrolyzers, including heat and mass transfer and system analysis. Finally, the book contains informative videos of industrial facilities, laboratory setups, and preparation procedures.