This study investigates the photodegradation of methylene blue (MB) using a UV/H₂O₂ system without a catalyst. The reaction variables, including the concentration of H₂O₂ and the initial MB concentration, were evaluated to determine the efficiency of the process. The degradation of MB was not observed in the dark, but increased with UV irradiation and H₂O₂ concentration. The degradation time decreased after reaching an optimal H₂O₂ concentration, and the rate of degradation became inversely proportional to H₂O₂ concentration as it began to scavenge hydroxyl radicals. Increasing the amounts of MB and H₂O₂ improved degradation efficiency due to enhanced oxidation. Experimental data were well-fitted to zero-order reaction kinetics, indicating that the degradation process follows a zero-order model. The mechanism involves the generation of hydroxyl radicals (OH·) and oxygen radicals (O₂·⁻) from H₂O₂ breakdown, which attack MB molecules, leading to their degradation into CO₂ and H₂O. The UV/H₂O₂ system proved efficient for MB degradation without a solid catalyst and can be applied to other organic pollutants in industrial wastewater. The study highlights the effectiveness of the UV/H₂O₂ system in degrading MB under various conditions and suggests further research using different light sources and reactors.This study investigates the photodegradation of methylene blue (MB) using a UV/H₂O₂ system without a catalyst. The reaction variables, including the concentration of H₂O₂ and the initial MB concentration, were evaluated to determine the efficiency of the process. The degradation of MB was not observed in the dark, but increased with UV irradiation and H₂O₂ concentration. The degradation time decreased after reaching an optimal H₂O₂ concentration, and the rate of degradation became inversely proportional to H₂O₂ concentration as it began to scavenge hydroxyl radicals. Increasing the amounts of MB and H₂O₂ improved degradation efficiency due to enhanced oxidation. Experimental data were well-fitted to zero-order reaction kinetics, indicating that the degradation process follows a zero-order model. The mechanism involves the generation of hydroxyl radicals (OH·) and oxygen radicals (O₂·⁻) from H₂O₂ breakdown, which attack MB molecules, leading to their degradation into CO₂ and H₂O. The UV/H₂O₂ system proved efficient for MB degradation without a solid catalyst and can be applied to other organic pollutants in industrial wastewater. The study highlights the effectiveness of the UV/H₂O₂ system in degrading MB under various conditions and suggests further research using different light sources and reactors.