The unabated release of herbicide imazapyr into the soil and groundwater led to crop destruction and several pollution-related concerns. In this contribution, heterogeneous photocatalytic technique was employed utilizing mesoporous Ga2O3-TiO2 nanocomposites for degrading imazapyr herbicide as a model pollutant molecule. Mesoporous Ga2O3-TiO2 nanocomposites with varied Ga2O3 contents (0-5 wt%) were synthesized through sol-gel process. XRD and Raman spectra exhibited extremely crystalline anatase TiO2 phase at low Ga2O3 content which gradually reduced with the increase of Ga2O3 content. TEM images display uniform TiO2 particles (10 +/- 2 nm) with mesoporous structure. The mesoporous TiO2 exhibits large surface areas of 167 m(2) g(-1), diminished to 108 m(2) g(-1) upon 5% Ga2O3 incorporation, with tunable mesopore diameter in the range of 3-9 nm. The photocatalytic efficiency of synthesized Ga2O3TiO2 nanocomposites was assessed by degrading imazapyr herbicide and comparing with commercial photocatalyst UV-100 and mesoporous Ga2O3 under UV illumination. 0.1% Ga2O3-TiO2 nanocomposite is considered the optimum photocatalyst, which degrades 98% of imazapyr herbicide within 180 min. Also, the photo degradation rate of imazapyr using 0.1% Ga2O3-TiO2 nanocomposite is nearly 10and 3-fold higher than that of mesoporous Ga2O3 and UV-100, respectively. The high photonic efficiency and long-term stability of the mesoporous Ga2O3-TiO2 nanocomposites are ascribed to its stronger oxidative capability in comparison with either mesoporous TiO2, Ga2O3 or commercial UV-100. (C) 2017 Elsevier B.V. All rights reserved.