This study investigates the photodegradation of methylene blue (MB) in water using a UV/H₂O₂ irradiation system without the need for a catalyst. The reaction variables, including the amount of H₂O₂ and the initial concentration of MB, were evaluated to assess the performance of the photodegradation process. The results show that MB degradation was not observed in the dark, and the degradation time decreased as the H₂O₂ concentration increased after reaching an optimal level. Beyond this point, the degradation rate became inversely proportional to the H₂O₂ concentration as it started to scavenge hydroxyl radicals. Increasing the concentrations of MB and H₂O₂ improved the degradation efficiency due to the enhanced oxidation process facilitated by the appropriate amount of H₂O₂ and an optimal duration of UV exposure. The experimental data were well-fitted to zero-order reaction kinetics, indicating that the degradation process is primarily influenced by the concentration of H₂O₂. The photodegradation mechanism involves the generation of hydroxyl radicals (OH•) and O₂•− species, which attack MB molecules, producing MB radicals (MB•) that undergo oxidation and ultimately convert to CO₂ and H₂O. The UV/H₂O₂ system proved to be efficient for the photodegradation of low-concentration MB solutions without the use of solid catalysts, making it suitable for degrading other organic pollutants in industrial wastewater.This study investigates the photodegradation of methylene blue (MB) in water using a UV/H₂O₂ irradiation system without the need for a catalyst. The reaction variables, including the amount of H₂O₂ and the initial concentration of MB, were evaluated to assess the performance of the photodegradation process. The results show that MB degradation was not observed in the dark, and the degradation time decreased as the H₂O₂ concentration increased after reaching an optimal level. Beyond this point, the degradation rate became inversely proportional to the H₂O₂ concentration as it started to scavenge hydroxyl radicals. Increasing the concentrations of MB and H₂O₂ improved the degradation efficiency due to the enhanced oxidation process facilitated by the appropriate amount of H₂O₂ and an optimal duration of UV exposure. The experimental data were well-fitted to zero-order reaction kinetics, indicating that the degradation process is primarily influenced by the concentration of H₂O₂. The photodegradation mechanism involves the generation of hydroxyl radicals (OH•) and O₂•− species, which attack MB molecules, producing MB radicals (MB•) that undergo oxidation and ultimately convert to CO₂ and H₂O. The UV/H₂O₂ system proved to be efficient for the photodegradation of low-concentration MB solutions without the use of solid catalysts, making it suitable for degrading other organic pollutants in industrial wastewater.