We report single-crystalline mesoporous molybdenum nitride nanowires (meso-Mo3N2-NWs) prepared by topotactic reaction using single-crystalline molybdenum oxide nanowires. The single-crystalline nature of meso-Mo3N2-NWs was clearly observed by field-emission transmission electron microscopy. The meso-Mo3N2-NWs exhibited mesoporous structure with similar to 45 m2/g in specific surface area and 4.6 nm in average pore size confirmed by a nitrogen sorption measurement. Due to high specific surface area and mesoporous structure, meso-Mo3N2-NWs showed much higher specific capacitance and excellent chargingdischarging performance as compared with Mo3N2 prepared using conventional nitridation process.