In this study, we evaluated the oxidation resistance of austenitic stainless steels 316L and 310S in two different environments: air at 600°C and atmospheric pressure and supercritical water at 600°C and pressure of 25 MPa. Results indicated that both alloys showed good oxidation resistance in air by producing a protective oxide layer on their surface. In addition, alloy 310S exhibited lower weight gain during air oxidation compared to alloy 316L due to its higher content of chromium and nickel. Oxidation of alloy 310S in supercritical water was much lower than that of alloy 316L because of the formation of a protective layer of spinel on the surface. No protective scale was formed on the surface of the alloy 316L, as magnetite () and iron-chromium spinel () were the product of oxidation in supercritical water.