A novel method for synthesizing nanomaterials involves microbial or phytochemical nano-factories, which offer an eco-friendly, cost-effective, and reliable approach to producing clean and reproducible products. In this study, magnesium oxide nanoparticles (MgO NPs) were synthesized using Avicennia marina, a marine plant, as both a nucleation and stabilizing agent. The MgO NPs were characterized for crystallinity, cut-off wavelength, morphology, thermal stability, and surface properties using XRD, EDX, BET, UV-Visible spectroscopy, DLS, zeta potential analysis, SEM, TEM, TGA/DTA, and PL spectroscopy. Using the Brunauer-Emmett-Teller (BET) method, the specific surface area of the MgO nanoparticles was determined to be 97.248 m