Shape-controlled gold nanostructures were successfully synthesized in an aqueous solution by a one-step, non-templated thermal reduction method through heating of a poly(vinylpyrrolidone)/HAuCl4 aqueous solution. Poly(vinylpyrrolidone) (PVP) serves as both the stabilizing surfactant and reducing agent for the controlled synthesis of gold nanostructures with different shapes. Upon adjusting the chain-length and the concentration of the PVP, decahedral, icosahedral and platelike gold nanostructures with dominating distribution were fabricated, respectively, with the ratio of terminating OH groups at the polymer to Au ions as an important experimental parameter. The results suggest that the morphology of the gold nanostructures could be tuned by this method. The successful preparation of gold nanostructures exemplifies a very facile, effective, and generic strategy for fabrication of gold nanoparticles with various shapes.