This chapter presents a comprehensive overview of the integration of green nanotechnology in the bioenergy sector, emphasizing its potential to enhance efficiency, environmental performance, and long-term sustainability. Green nanotechnology, defined using environmentally benign materials and energy-efficient processes, has become increasingly relevant in addressing the limitations of conventional bioenergy systems. With rising global energy demand and the need to reduce greenhouse gas emissions, innovations at the nanoscale offer promising solutions for cleaner and more effective energy production from biomass. The chapter explores a range of applications where nanomaterials contribute significantly to bioenergy processes. These include nanocatalysts that accelerate biodiesel synthesis, nano-adsorbents that improve biomass pretreatment, and nanostructures that enhance microbial activity in anaerobic digestion and algal biofuel systems. Emphasis is placed on performance improvements such as higher bioconversion rates, increased gas yields, improved reaction kinetics, and the stability and reusability of nanomaterials. Furthermore, the environmental and energy impacts of nano-enabled bioenergy are evaluated using life cycle analysis (LCA) and carbon footprint comparisons. While the benefits are considerable, the chapter also addresses critical challenges, including nanotoxicity, material safety, regulatory uncertainty, and public perception. Ethical considerations and ecological risks are acknowledged as key concerns in the widespread deployment of nanomaterials. In conclusion, the chapter outlines a future innovation roadmap focused on biodegradable nanomaterials, scalable synthesis methods, smart sensor integration, and collaborative governance. It concludes that, when guided by sustainability principles and responsible innovation, the fusion of nanotechnology with bioenergy systems can become a cornerstone of the global transition toward a cleaner and more resilient energy future.