The growing need for sustainable alternatives have prompted intensive research into bio-based materials. However, traditional bio-based materials often suffer from limitations such as poor mechanical strength, low barrier performance, and limited functional properties, hindering their broader industrial application. To overcome these shortcomings, nanotechnology has emerged as a powerful tool that can significantly enhance the performance, functionality, and sustainability of bio-based materials. This chapter explores the integration of nanotechnology into bio-based systems, introducing the fundamental concepts of nanomaterials, nanoparticles, and nanoscale structures. It presents a comprehensive overview of synthesis methods, including top-down, bottom-up, and green synthesis approaches, and highlights how these influence the morphology, stability, and functional properties of nanomaterials. The convergence of nanotechnology and bio-based resources has led to the development of advanced nanocellulose, nanoclays, metal/metal oxide nanoparticles, carbon-based nanomaterials, and nanocatalysts in which each examined for their structural characteristics, preparation techniques, and real-world applications. The chapter also addresses sustainability considerations through eco-friendly synthesis strategies, life cycle analysis, and the challenges of disposal and recycling. Safety and toxicological concerns related to human health and environmental exposure are critically reviewed alongside international nano-safety guidelines. This chapter thus offers an integrated perspective on how nanotechnology is reshaping the future of bio-based materials, bridging the gap between material innovation and sustainable development.