<p>This research focuses on the sustainable green synthesis of iron oxide nanoparticles (Fe₃O₄NPs) using the leaf extract of <i>Ficus religiosa</i> (FR). The Fe₃O₄NPs displayed a UV–visible absorption peak at 350&#xa0;nm, and XRD confirmed their crystalline nature. FTIR analysis demonstrated the presence of diverse functional groups responsible for the bioreduction of Fe₃O₄NPs. The SEM results revealed that Fe₃O₄NPs were spherical, and the EDX spectrum showed prominent peaks of iron and oxygen. Fe₃O₄NPs demonstrated significant antioxidant potential, with 68% TAA, 78% H₂O₂, and 66% DPPH radical scavenging activities at a concentration of 150&#xa0;µg/mL. The IC₅₀ values of FR-Fe₃O₄NPs were found to be 89&#xa0;µg/mL for TAA; 80&#xa0;µg/mL for H₂O₂ scavenging, and 96&#xa0;µg/mL for DPPH radical scavenging activity. Furthermore, the Fe₃O₄NPs exhibited potential antibacterial activity against pathogenic bacteria. FR-Fe₃O₄NPs degraded 90% of methylene blue within 120&#xa0;min. Thus, this study promotes eco-friendly, cost-effective synthesis with broad applications.</p> Graphical Abstract <p></p>