In this paper, a facile, template-free, one-step solvothermal method to synthesize size- and shape-controllable α-GaOOH with hierarchical nanoarchitectures has been developed. Hyperbranched α-GaOOH nanocrystals with a sheaf-like morphology has been prepared via the alcoholysis process with GaCl₃ and methanol as the reactants in the presence of benzene as solvent at 160 °C within an autoclave. For the formation of α-GaOOH hierarchical nanoarchitectures, the crystal splitting growth mechanism plays the dominant role, which has been evidenced by the characterization of the time-dependent morphologies of the prepared samples. The UV-vis absorption spectra recorded at room temperature reveal that the obtained nanostructured α-GaOOH is a direct band gap semiconductor and the band gap E_g is estimated to be about 5.24 eV. Furthermore, a broad PL emission band can be clearly observed in the 425 to 575 nm spectrum range for the synthesized hyperbranched sheaf-like α-GaOOH nanoarchitectures.