The eco-friendly synthesis of metal and metal oxide nanoparticles has garnered considerable interest due to its sustainable production techniques. This method employs natural reducing agents, including plant extracts, bacteria, and other biogenic materials, to synthesize nanoparticles with distinctive characteristics. Metal nanoparticles, including copper (CuNPs) and silver (AgNPs), gold (AuNPs), together with metal oxide NPs such as titanium dioxide (TiO₂), iron oxide (Fe₃O₄, Fe₂O₃), and zinc oxide (ZnO), are produced by these environmentally friendly procedures. The nanoparticles display diverse qualities such as elevated surface area, biocompatibility, and catalytic activity, rendering them appropriate for several applications in biomedical, environmental, agricultural, and industrial sectors. In biomedical applications, green-synthesized nanoparticles are investigated for their potential in drug delivery, antimicrobial properties, and cancer treatment. In the environmental sector, they are utilized for water purification, wastewater treatment, and air pollution mitigation. Additionally, they have potential applications in agriculture for improved pesticide administration and plant development, alongside industrial usage in catalysis, sensing, and electronics. Notwithstanding the myriad advantages, obstacles including scalability, stability, and toxicity issues persist. The future of green nanoparticle synthesis depends on addressing these issues, enhancing synthesis methodologies, and guaranteeing sustainable manufacturing methods for various applications.