Single-phase hexagonal sodium tungsten bronze (h-Na x WO 3 þ x/2 Á yH 2 O) was synthesized via a microwave-assisted hydrothermal method. A reaction time of 4 min was sufficient to obtain well-crystallized nanoplates with a thickness of 5-16 nm and length of 5-500 nm. The structure, morphology, and composition of the obtained material were characterized by X-ray diffraction and scanning electron microscopy. H 2 O molecules and Na species were detected in the hexagonal channels of the tungsten bronze structure. The gas sensing properties were also measured, suggesting that h-Na x WO 3 þ x/2 Á yH 2 O can be a promising material for NO 2 detection due to the high response observed.