Single-atom catalysts (SACs) are highly effective in electrochemical energy conversion due to their abundant active sites. Their exceptional electrocatalytic efficiency can be achieved by regulating the electronic structure to optimize the binding energy of intermediates and reduce the energy barrier of electrocatalytic reactions. This is achieved through the metal–support interaction at the interface of SACs. Controlling the electronic structure at the atomic level is a promising strategy for promoting activity, selectivity, and stability. To further understand the influence of electronic structure and accelerate the development of SACs, we summarize various fabrication strategies to construct SACs and further adjust the electronic structure to achieve excellent hydrogen/oxygen evolution and O₂/N₂/CO₂ reduction reactions. Finally, we discuss the challenges and prospects of SACs for controllable electrocatalytic processes and provide guidance for the future exploration of electrochemical energy conversion.