The growing demand for high-performance energy storage systems has driven the development of advanced materials to improve supercapacitor efficiency. In this study, MXene-MnNi nanocomposites are synthesized and evaluated for their potential as next-generation supercapacitor electrodes. The MnNi alloy, known for its excellent pseudocapacitive properties, is combined with MXene, a two-dimensional material recognized for its exceptional conductivity, mechanical robustness, and large surface area. The uniform dispersion of MnNi and MXene achieved through a straightforward hydrothermal method, optimizes charge transfer and enhances electrochemical performance. Electrochemical testing demonstrates that the 100 MX-MN nanocomposite exhibits a high specific capacity of 1028 C g-1 at 1 A g-1, along with excellent rate capability and long-term stability, outperforming many conventional materials. This outstanding performance is attributed to the synergistic effects of MnNi’s redox activity and MXene’s high conductivity, which together increase active site availability, accelerate ion diffusion, and maintain structural integrity. Additionally, a hybrid aqueous device is assembled using 100 MX-MN as the positive electrode and activated carbon as the negative electrode. The device delivers a maximum energy density of 87.35 W h kg-1 at a power density of 1.98 kW kg-1 and exhibits excellent capacity retention of 88 % after 10,000 charge-discharge cycles. These findings highlight the potential of MXene-MnNi nanocomposites as advanced materials for supercapacitor applications, offering a promising path for more efficient energy storage solutions in modern electronic devices.