The kinetics of ozonation of the sulfur dye Methylene Blue in aqueous solution is studied. The experiments have been carried out in a bubble column, using a single nozzle as gas sparger. The influence of the operating variables (initial concentration of Methylene Blue, ozone partial pressure, temperature and pH) on the oxidation process is established. A stoichiometric ratio of 3 moles of ozone consumed per mol of dye reacted is deduced. A reaction scheme based on the direct ozone attack to the dye is suggested, and it agrees with the found stoichiometry. The overall reaction orders and rate constants as a function of pH and temperature are determined following the film theory which is applied to the experimental data. The process develops in the fast pseudo mth order kinetic regime of absorption.