RuO2@Na-Y zeolite is a highly active catalyst for the selective catalytic oxidation of NH3 into N2 at relatively low temperatures. RuO2@Na-Y zeolite achieved the stoichiometric conversion of NH3 into N2 at 175 °C in the presence of water vapor and CO2. Increasing the reaction temperature led to the formation of more-oxidized reaction products (N2O, NO, and NO2). This catalyst was successfully operated in a cycling mode with alternating ammonia- and oxygen-containing gas streams. As expected, the catalyst was only poorly efficient in the selective catalytic reduction of ammonia.