The conversion of biomass waste into porous carbon for supercapacitor electrode applications represents a highly promising and sustainable approach due to its low cost, abundance of raw materials, and environmental benefits. In this work, activated carbon (AC) was synthesized from Lapsi (Choerospondias axillaris) seed biomass through a chemical activation process using zinc chloride (ZnCl₂) as an activating agent, followed by carbonization in a tubular furnace at 850 °C under a continuous nitrogen flow of 100 cc/min for 4 hours. The resulting activated carbon, with its porous structure, was then explored as a potential electrode material for supercapacitors. Electrochemical performance was systematically examined in a three-electrode setup using a potentiostat, employing cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) to obtain a comprehensive understanding of its behavior. Key parameters such as specific capacitance, charge–discharge stability, and impedance were carefully evaluated. The electrode achieved a specific capacitance of 71.95 F/g at a current density of 1 A/g and demonstrated remarkable cycling stability, retaining 95.71% of its capacitance even after 5000 consecutive charge–discharge cycles. These findings clearly underline the potential of Lapsi seed-derived activated carbon as a low-cost, environmentally friendly, and durable electrode material, offering a sustainable pathway toward the development of next-generation supercapacitor technologies.