The green synthesis of metallic nanoparticles (MNPs) using plant-based materials offers a sustainable alternative to chemical methods and holds great promise in biomedical applications, particularly for combating antibiotic-resistant pathogens. In this study, rosemary (Rosmarinus officinalis), known for its rich phytochemical profile with antimicrobial and antioxidant properties, was used as both a reducing and stabilizing agent in nanoparticle synthesis. Rosemary extract was prepared and analyzed for its bioactive constituents using gas chromatography–mass spectrometry (GC-MS), and its antioxidant and antimicrobial activities were evaluated. The extract was then employed in the green synthesis of MNPs. The resulting nanoparticles are currently being characterized using UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and dynamic light scattering (DLS) to determine their optical, structural, and morphological properties. Preliminary results have confirmed the presence of key phytochemicals, particularly phenolic and terpenoid compounds, that facilitate metal ion reduction and nanoparticle stabilization. UV-Vis analysis indicated successful nanoparticle formation, and antimicrobial assays demonstrated promising activity against pathogenic bacterial strains. These findings highlight rosemary extract as an effective and eco-friendly agent for producing biologically active MNPs, supporting their potential as novel antibacterial agents in the fight against antibiotic resistance. This approach also not only reduces the use of hazardous chemicals but also enhances antimicrobial efficacy by combining the properties of both metal ions and plant-derived compounds.