We report single-crystalline TiO2 nanowires (TiO2-NWs) synthesized by hydrothermal process without any surfactant and template with enhanced lithium intercalation properties. The single-crystalline nature of rutile TiO2-NWs was clearly observed by field-emission transmission electron microscopy and fast Fourier transform pattern demonstrating that the nanowire growth is along the [001] direction. The single-crystalline rutile TiO2-NWs showed much higher charge capacity and excellent high-rate performance as compared to typical rutile TiO2 nanoparticles. The improved lithium-ion intercalation properties of TiO2-NWs may be attributed to relatively large specific surface area, short transport distance of 1-D nanostructure, and freedom for volume change accompanied by lithium-ion intercalation.