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Supported gold catalysts are highly active for a variety of reactions, including low‐temperature CO oxidation. It has been shown that reducible support materials, for example, ceria and titania, may significantly alter catalytic performance. However, the current understanding of the CO oxidation mechanism of such gold catalysts is still incomplete, as important details such as the activation of oxygen and the role of oxygen vacancies are unknown. To elucidate the role of the ceria support during room‐temperature CO oxidation, we employed operando Raman spectroscopy by simultaneously recording the Raman spectra of the catalyst and the gas‐phase FTIR spectra. Our results give first direct spectroscopic evidence for the participation of oxygen vacancies in the oxidation of CO over ceria‐supported gold, which thus underlines the crucial role of the support material for detailed understanding of the mode of operation of supported gold catalysts.