Abstract Single-crystalline gallium oxide hydroxide (α-GaOOH) nanorods could be successfully synthesized in large quantities through a hydrothermal synthetic method using gallium oxide as the gallium source and sodium azide and aqueous hydrazine as both alkaline and complexing reagent. Single-crystalline gallium oxide (α-Ga 2 O 3 and β-Ga 2 O 3 ) nanorods could be selectively obtained by thermal decomposition method using gallium oxide hydroxide nanorods as the precursor. The phase structures, morphologies and properties of the final products were investigated in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), selected area electron diffraction (SAED), fourier transform infrared spectra (FTIR), differential scanning calorimetric analysis (DSC), thermogravimetric analysis (TG), and photoluminescence spectra (PL).