A three-dimensional hierarchical porous carbon is synthesized via a facile chemical activation route with garlic skin as the precursor and KOH as the activating agent. The as-obtained carbon presents a high specific surface area of 2818 m2 g-1 and a hierarchical porous architecture containing macroporous frameworks, mesopores (2-4 nm), and micropores (0.6-1.0 nm). As the electrode material for a supercapacitor, due to its unique interconnected porous structure, this garlic skin-derived carbon exhibits excellent electrochemical performance and cycling stability. At a current density of 0.5 A g-1, the capacitance is up to 427 F g-1 (162 F cm-3). Even at a high current density of 50 A g-1, the capacitance can be maintained to a high value of 315 F g-1 (120 F cm-3). After charging-discharging at a current density of 4.5 A g-1 for 5000 cycles, the capacitance retention is as high as 94%. The results suggest that this garlic skin-derived 3D hierarchical porous carbon is a promising electrode material for high-performance supercapacitors.