Vertically aligned TiO 2 nanotube arrays for H 2 gas sensor were fabricated by using atomic layer deposition combined with anodic aluminum oxide template. Morphology and crystalline structure of the TiO 2 nanotubes were characterized, and gas sensing properties at low temperatures (<200°C) were investigated. Uniform TiO 2 nanotubes with anatase phase were synthesized to be vertically aligned on the substrate and electrically interconnected with each other. The TiO 2 nanotube sensors were operated in air environment, and the highest magnitude of the gas response (R air /R gas ) was determined to be ∼100 toward 1000ppm H 2 /air at 100°C. The sensor showed a very short response time (<1s) and a high selectivity for H 2 gas against several reducing gases including NH 3 , CO, and C 2 H 5 OH.