A highly efficient, carbon-free rice husk ash (RHA) has been successfully used as a catalyst in oxalic acid (OA) decomposition by combining with ozonation at pH 3. The catalyst was characterized using various analytical techniques. X-ray fluorescence (XRF) analysis showed that RHA catalyst contains SiO2, as a major constituent and MgO, P2O5, SO3, K2O, CaO, MnO2, Fe2O3, CuO, ZnO as minor constituents. X-ray diffraction (XRD) and EDX analysis consistently confirmed the presence of silica as a major constituent. Cold field scanning electron microscopic (FESEM) analysis revealed nonuniform particle size and the presence of external pores on the catalyst surface. Elemental analysis (EA) indicated that RHA contains negligible percentage of carbon content. Oxalic acid degradation as well as its TOC removal was studied at various physicochemical conditions. Adsorption and ozonation processes are not effective for oxalic acid and its TOC removal. The addition of RHA catalyst in the ozonation process caused 76.2% OA decomposition and 75% TOC removal in 60 min. Also, 0.25 g/L RHA dosage was found to be optimum for effective removal of oxalic acid. The efficiencies of RHA was compared with other commercially. available catalysts, and the order was found to be RHA approximate to TiO2-P25 > FeOOH > SiO2 > Al2O3 > ZnO. Oxalic acid decomposition was enhanced by increasing inlet gaseous ozone concentration from 40 to 120 mg/L. The catalytic ozonation process is more pronounced than the ozonation process alone at pH 3, 7, and 10. It is concluded that RHA is an efficient green catalyst for oxalic acid removal.