The present invention relates generally to catalysts comprising ruthenium oxide and to processes for catalyzing the oxidation and conversion of sulfur dioxide (SO 2 ) to sulfur trioxide (SO 3 ) using such catalysts. SO 2 at low concentrations in process gas streams can be effectively oxidized to SO 3 at relatively low temperatures using the ruthenium oxide catalysts of the present invention. In one application, the ruthenium oxide catalysts are used in the final contact stage for conversion of SO 2 to SO 3 in multiple stage catalytic converters used in sulfuric acid manufacture.