Novel Au@TiO₂ plasmonic films were fabricated by individually placing Au nanoparticles into TiO₂ nanocavity arrays through a sputtering and dewetting process. These discrete Au nanoparticles in TiO₂ nanocavities showed strong visible-light absorption due to the plasmonic resonance. Surface-enhanced Raman spectra (SERS) of this plasmonic film showed a high sensityvity to organic molecule at low concentration (down to 0.1 micro molar). Photoelectrochemical studies demonstrated that the developed Au@TiO₂ plasmonic films exhibited significantly enhanced catalytic activities towards oxygen reduction reactions with an onset potential of 0.92 V (vs reversible hydrogen electrode), electron transfer number of 3.94, and limiting current density of 5.2 mA cm^-2. The deposited Au film thickness remarkably affected the catalytic activities of Au@TiO₂, and TiO₂ coated with 5 nm Au (Au₅@TiO₂) exhibited the best catalytic function to reduce oxygen. The plasmon-enhanced reductive activity is attributed to the surface plasmonic resonance of embedded Au nanoparticles in TiO₂ nanocavities and suppressed electron recombination.