The characteristics of a high-power single-chip blue light-emitting diode (LED) operating with >10 W input power are reported. The LED chip was fabricated in the form of a vertical-injection structure with chip dimensions of 1.8×1.8 mm. Electrode patterns at the n-GaN surface were designed to optimise the output power and operation voltage. Electrical and optical characteristics of the LED were measured up to 3 A injection current under pulsed operation condition. Output power and forward voltage at 3 A were obtained to be 3.3 W and 3.67 V, respectively, which demonstrates the wall-plug efficiency of >30% with 10 W input power. Even higher output power and efficiency are expected from the single-chip LED by reducing the efficiency droop of InGaN-based LEDs.