Rationally designed Mg₂WO₄ hierarchical super-architectures were successfully synthesized for multifunctional electrochemical energy storage and water-splitting applications. The reaction parameters were systematically optimized to retain the orthorhombic phase with a high batch yield (~6.5 g), leading to improved ion intercalation/de-intercalation behavior and enhanced electrochemical stability. The obtained porous layered architectures possessed mesoporous features with a large surface area, offering abundant active sites and efficient electrolyte penetration. The introduction of redox additives into the electrolyte remarkably enhanced the charge-storage performance, delivering a high specific capacitance of ~1490 F g⁻¹ at 1 A g⁻¹. The fabricated asymmetric solid-state supercapacitor exhibited an extended operating voltage window (~1.2 V), high energy density (~118 Wh kg⁻¹), excellent power performance, and superior cyclic durability over 10,000 cycles. Moreover, the Mg₂WO₄-based electrode demonstrated efficient electrocatalytic water-splitting activity with low OER/HER overpotentials of ~265/95.3 mV and long-term operational stability exceeding 30 h. The assembled symmetric alkaline electrolyzer further achieved a stable cell voltage of 1.52 V, confirming the excellent bifunctional electrochemical performance of the Mg₂WO₄ hierarchical super-architectures for next-generation sustainable energy applications.