The increased industrialization of industries such as textiles, leather, and paper manufacturing has resulted in significant water pollution caused by the discharge of persistent synthetic dyes. In this study, yttrium-loaded ZnO (Y-ZnO) nanoparticles were synthesized to enhance photocatalytic efficiency and antibacterial properties. Yttrium incorporation not only improved visible light absorption, reducing the bandgap to 3.16 eV for 3 wt% YZnO, but also introduced beneficial surface defects, as confirmed by photoluminescence, UV-DRS, and XPS analyses. The photocatalytic activity of the materials was assessed through the degradation of Reactive Red 120 (RR 120) dye under UV-A and solar irradiation. Notably, 3 wt% Y-ZnO achieved complete degradation of RR 120 within 30 min under UV-A light and nearly 100 % under sunlight within 70 min at pH 11. Reusability studies demonstrated excellent stability, with 92.3 % efficiency retained after four cycles. Trapping experiments revealed that superoxide radicals (O2 center dot-) were the dominant reactive species, followed by holes (h+), electrons (e-), and hydroxyl radicals (center dot OH). Gas chromatography-mass spectrometry (GC-MS) analyses elucidated the degradation pathway of RR 120. Furthermore, antibacterial assays showed significant inhibition zones (8-10 mm) against Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis, and Escherichia coli at a concentration of 100 mu g/mL. The dual photocatalytic and antibacterial functionalities of Y-ZnO present a promising strategy for sustainable wastewater treatment and biomedical applications.