Abstract: Attaining a decarbonized and sustainable energy system, which is the core solution to global energy issues, is accessible through the development of hydrogen energy. Proton-exchange membrane water electrolyzers (PEMWEs) are promising devices for hydrogen production, given their high efficiency, rapid responsiveness, and compactness. Bipolar plates account for a relatively high percentage of the total cost and weight compared with other components of PEMWEs. Thus, optimization of their design may accelerate the promotion of PEMWEs. This paper reviews the advances in materials and flow-field design for bipolar plates. First, the working conditions of proton-exchange membrane fuel cells (PEMFCs) and PEMWEs are compared, including reaction direction, operating temperature, pressure, input/output, and potential. Then, the current research status of bipolar-plate substrates and surface coatings is summarized, and some typical channel-rib flow fields and porous flow fields are presented. Furthermore, the effects of materials on mass and heat transfer and the possibility of reducing corrosion by improving the flow field structure are explored. Finally, this review discusses the potential directions of the development of bipolar-plate design, including material fabrication, flow-field geometry optimization using three-dimensional printing, and surface-coating composition optimization based on computational materials science.