[en] The kinetics of the homogeneous gas-phase oxidation of tritium (2T₂ + O₂ → 2T₂O) have been studied by use of a model which accounts explicitly for the radiolysis of the major species and the kinetics of the subsequent reactions of the ionic, excited-state, and neutral species. This report includes a detailed calculation of the radiolysis product distribution due to the tritium β decay with special attention given to oxygen radiolysis. Adjustments were made to hydrogen-based rate constants obtained from the literature to account for kinetic isotope effects. Results from model calculations are given for 10^-4-1.0 mol % pure T₂ in pure O₂ at 298 K and 1 atm, from time of mixing to beyond the 1/e conversion time. As the reaction evolves, three different mechanisms control the T₂O production. Each mechanism has a different overall rate expression with a different order with respect to the T₂ concentration. From the predicted mechanisms the importance of the radiolysis products and subsequent ion reaction is evident