<p>This review provides a critical and forward-looking analysis of recent advancements in magnesium-based electrode materials for supercapacitors, a class of materials distinguished by their unique combination of high theoretical capacity, divalent charge carrier (Mg²⁺), and sustainability profile. Moving beyond a simple summary, the work systematically deconstructs the electrochemical performance and charge storage mechanisms of key material families, including oxides (e.g., MgCo₂O₄, MgO), hydroxides, sulfides, and hybrid composites by linking specific structural modifications (nanostructuring, doping, composite formation) to their resultant impact on conductivity, stability, and capacitance. A central and unique contribution of this review is its structured critical evaluation, which clearly delineates the persistent challenges of poor intrinsic conductivity and ion diffusion kinetics, and their direct consequences on device-level performance. Furthermore, the review merges current literature into actionable, strategic research pathways. It prioritizes advanced material engineering, such as the design of conductive 3D heterostructures and defect-controlled doping, to chart a clear course for overcoming existing limitations. Ultimately, this work positions magnesium-based electrodes not merely as alternatives but as a viable and sustainable platform for next-generation energy storage, provided these focused research directions are pursued.</p>