AbstractRechargeable magnesium batteries hold promise for providing high energy density, material sustainability, and safety features, attracting increasing research interest as post‐lithium batteries. With the progressive development of Mg electrolytes with enhanced (electro‐)chemical stability, tremendous efforts have been devoted to the exploration of high‐energy cathode materials. In this review, recent findings related to Mg cathode chemistry are summarized, focusing on the strategies that promote Mg²⁺ diffusion by targeting its interaction with the cathode hosts. The critical role of the cathode–electrolyte interfaces is elaborated, which remains largely unexplored in Mg systems. The approaches to optimization of cathode–electrolyte combinations to unlock the kinetic limitations of Mg²⁺ diffusion, enabling fast electrochemical processes of the cathodes, are highlighted. Furthermore, representative conversion chemistries and coordination chemistries that bypass bulk Mg²⁺ diffusion are discussed, with particular attention given to their key challenges and prospects. Finally, the hybrid systems that combine the fast kinetics of the monovalent cathode chemistries and high‐capacity Mg anodes are revisited, calling for further practical evaluation of this promising strategy. All in all, the aim is to provide fundamental insights into the cathode chemistry, which promotes the material development and interfacial regulations toward practical high‐performance Mg batteries.