Fuel cells directly convert the chemical energy of the fuel and oxidant (typically air) into electricity with waste heat and water as the only reaction byproducts. As a clean power generator, fuel cell has been vehemently developed for practical applications due to concerns related to the emissions of chemical pollutants and greenhouse gases associated with conventional combustion-based power generation. Fuel cells, especially proton exchange membrane (PEM) fuel cells, have reached early stage of commercialization, with further technical requirements on improvement in performance and durability/reliability as well as on cost reduction. This special issue is targeted to report the progresses made in fuel cells, including fundamental understanding, development of key materials such as low-Pt and non-Pt catalysts and bipolar plates, design and optimization of catalyst layers, membrane-electrode assemblies, single cells, stacks and power systems as well as practical applications and technology demonstrations. State-of-the-art and original contributions involving experimental and numerical studies, recent developments, and novel and emerging technologies in this field are highly encouraged.