<p>This study presents a comprehensive investigation on the green synthesis of selenium nanoparticles using aloe vera extract as a reducing and stabilizing agent for photocatalytic applications. The research addresses the need for environmentally friendly synthesis methods and explores the potential of selenium nanoparticles in photocatalysis. Different concentrations of selenium nanoparticles were prepared while maintaining a constant concentration of aloe vera extract. The synthesized nanoparticles were characterized using UV spectroscopy, FTIR spectroscopy, XRD, and SEM. Photocatalytic experiments were conducted using methylene blue (MB) dye as a model pollutant and photocatalysis was performed under natural sunlight irradiation and without any co-catalyst or artificial light source for 70&#xa0;min. The results highlight the efficient photocatalytic degradation of MB dye by the selenium nanoparticles prepared using aloe vera extract, with the degradation efficiency of 99.39%. This study contributes to the understanding of green synthesis approaches and the exceptional potential of selenium nanoparticles for real-world conditions in photocatalytic application.</p> Graphical Abstract <p></p>