<p>High-entropy oxides have emerged as a transformative class of materials for next-generation energy storage; however, rational incorporation of heavy 5d elements to simultaneously modulate electronic, ionic, and magnetic properties remains largely unexplored. In this work, we report a defect-engineered 5&#xa0;mol% osmium-doped (CoCrFeMnNi)₃O₄ high-entropy spinel synthesized via a controlled sol–gel strategy, enabling homogeneous cation distribution and entropy-driven phase stabilization. Structural analysis confirms the formation of a single-phase cubic spinel with subtle lattice expansion upon osmium incorporation, while microstructural investigations reveal highly crystalline nanostructures with coherent lattice fringes and uniform dopant dispersion. Electrochemical studies demonstrate a hybrid charge storage mechanism combining diffusion-controlled faradaic reactions and surface capacitive contributions, delivering excellent rate capability, low internal resistance, and high reversibility. The linear dependence of peak current on the square root of scan rate evidences efficient ion transport kinetics, while impedance analysis confirms enhanced charge-transfer dynamics induced by 5d orbital interactions. Furthermore, the material exhibits soft ferromagnetic behavior at room temperature, highlighting its multifunctional potential. The synergistic interplay of configurational entropy, defect engineering, and osmium-induced electronic modulation establishes this system as a promising platform for sustainable, high-performance energy storage and magneto-electronic applications aligned with global energy and industrial innovation goals. Also, this work directly supports SDG (Affordable and Clean Energy) and (Industry, Innovation and Infrastructure) by advancing entropy-engineered multifunctional electrode materials for sustainable high-performance energy storage and next-generation smart electrochemical technologies.</p>