In this study, we examined the experimental catalytic oxidation of gaseous monochlorobenzene (MCBz) with O3 over Fe2O3 in a packed bed reactor to investigate the feasibility of economical low temperature decomposition at a high space velocity (SV). We investigated the effects of several reaction parameters (temperature, O3 concentration, and SV) on the MCBz oxidation. At 150°C, the conversion of MCBz over Fe2O3 in the absence of O3 was only 3%; it increased to 91% over Fe2O3 in the presence of 1200ppm of O3 at a high SV of 83s-1. A long-term operation study revealed that the conversion of MCBz was stable for more than 96h. In the steady state, the carbon and chlorine balances were 88% and 86%, respectively. Applying a Langmuir-Hinshelwood kinetic model, we estimated an activation energy of 16.7kJmol-1 for MCBz oxidation over Fe2O3 in the presence of O3.