Sulfuric acid is proposed as an inexpensive oxidant for use in the oxidative desulfurization (ODS) of petroleum. The oxidative extraction of thiophene, tetrahydrothiophene, and dibutyl sulfide by concentrated sulfuric acid in a two-liquid-phase reactor is demonstrated. The reaction proceeds rapidly at room temperature at sulfide concentrations greater than similar to 100 ppm S and yields sulfoxides, sulfonates, and other oxidized sulfur species as products. The oxidized sulfur species are effectively extracted into the acid phase. The reactions are first-order in sulfide at high acid concentrations and first-order in acid at lower acid concentrations. This technique might be able to reduce the load on hydrodesulfurization (HDS) or ODS reactors by pretreating high-sulfur feed streams.