Abstract We have synthesized gallium oxide (Ga 2 O 3 ) nanobelts by heating GaN powders in the conventional furnace. The nanobelts exhibited a unique bicrystalline structure that consisted of two single-crystalline monoclinic Ga 2 O 3 nanobelts, which split along the twin boundary that exists at the centerline. Energy dispersive X-ray spectroscopy and electron energy loss spectroscopy spectra coincidentally indicated the presence of nitrogen in the Ga 2 O 3 nanobelts. Photoluminescence spectra exhibited the visible light emission. We discussed the possible emission mechanisms, including the effect of the nitrogen dopant.