Nanostructured materials have emerged as game-changers in the field of sustainable energy, owing to their high surface area, tunable porosity, and superior functional properties that enable enhanced energy conversion and storage performance. Among these, nanostructured bio-aerogels derived from renewable biopolymers stand out for their ultra-lightweight structure, thermal stability, and biodegradability, positioning them as ideal candidates for eco-friendly energy technologies. This chapter explores the transformative potential of these materials, beginning with an overview of their synthesis and fabrication strategies tailored for energy-specific functions. It emphasizes how nanoscale engineering significantly enhances the functional efficiency of bio-aerogels in various energy domains. Key applications in energy conversion are thoroughly examined, including their roles in fuel cells, catalyst supports, electrolyte membranes, and solar energy systems, where their thermal insulation and optical properties prove valuable. The chapter also discusses thermoelectric applications that improve thermal-electric conversion efficiency. In the context of energy storage, the chapter highlights the integration of nanostructured bio-aerogels in supercapacitors, advanced electrode materials, hydrogen storage, and battery technologies ranging from lithium-ion to sodium- and zinc-ion systems. It concludes by reinforcing the pivotal role of nanostructured bio-aerogels in developing scalable, high-performance, and environmentally conscious energy solutions for a sustainable future.