Au nanoparticle decorated SrTiO3:Nb (Au/SrTiO3:Nb) has been demonstrated as a photoanode for photo-oxidation under visible light. The visible light photo-oxidation is a result of the generation of the hot electrons in the Au nanoparticles, which are subsequently injected into the SrTiO3:Nb conduction band. This leaves behind holes for electrochemical oxidation, which can oxidize a variety of chemical species with redox potentials ranging from 0 to 1.23 V vs RHE. The visible light response is most enhanced at the surface plasmon resonance energy of the Au nanoparticles, which we believe reflect the high optical density near the plasmon resonance for the sensitization. This work demonstrates a general route to impart visible light utilization to a wide band gap semiconductor for various energy conversion and environmental applications, including solar fuel generation and organic pollutant decomposition.