This research article describes the synthesis of MgO nanospheres using the successive ionic layer adsorption and reaction (SILAR) technique on stainless steel substrates. The optimized sample was characterized using XRD, which confirmed a cubic structure. Electrochemical characterization, including cyclic voltammetry (CV), chronopotentiometry, and electrochemical impedance spectroscopy (EIS), revealed a high specific capacitance (SC) of 536.06 F/g, with maximum specific energy and power of 30.79 Wh/kg and 1420 W/kg, respectively, at 2 mA/cm² in 1-M KOH. The EIS plot indicated an internal resistance (Ri) of 0.86 Ω, demonstrating good power performance and rate capability. The material showed excellent cycling capability, retaining 91.38% capacitance after 5000 CV cycles. The MgO/AC device exhibited an SC of 210.21 F/g at 5 mV/s in a PVA-KOH solid-state electrolyte, with an energy density of 23.90 Wh/kg and a power density of 1.84 kW/kg. After 5000 CV cycles, the supercapacitor device retained 92.93% capacitance. The study highlights the effectiveness of the SILAR method for synthesizing pure MgO nanostructures suitable for supercapacitor applications.This research article describes the synthesis of MgO nanospheres using the successive ionic layer adsorption and reaction (SILAR) technique on stainless steel substrates. The optimized sample was characterized using XRD, which confirmed a cubic structure. Electrochemical characterization, including cyclic voltammetry (CV), chronopotentiometry, and electrochemical impedance spectroscopy (EIS), revealed a high specific capacitance (SC) of 536.06 F/g, with maximum specific energy and power of 30.79 Wh/kg and 1420 W/kg, respectively, at 2 mA/cm² in 1-M KOH. The EIS plot indicated an internal resistance (Ri) of 0.86 Ω, demonstrating good power performance and rate capability. The material showed excellent cycling capability, retaining 91.38% capacitance after 5000 CV cycles. The MgO/AC device exhibited an SC of 210.21 F/g at 5 mV/s in a PVA-KOH solid-state electrolyte, with an energy density of 23.90 Wh/kg and a power density of 1.84 kW/kg. After 5000 CV cycles, the supercapacitor device retained 92.93% capacitance. The study highlights the effectiveness of the SILAR method for synthesizing pure MgO nanostructures suitable for supercapacitor applications.