The growing necessity for reducing environmental pollution and a shift towards a circular economy have prompted the advancement of sustainable macro, micro, and nanocomposites derived from biopolymers. This chapter provides an overview of biopolymer-based composites, focusing mainly on their various advanced applications. The importance of these composites is highlighted in critical sectors including packaging, construction, agriculture, automotive, biomedical applications, energy harvesting, aerospace, and wastewater treatment. The emerging innovations towards self-healing systems, shape-memory materials, and bio-based sensors are also discussed, addressing the challenges associated with durability, scalability, and economic feasibility of biopolymer-based composites. Thus, the scientific advancements, economic feasibility, and industrial potential of sustainable composites establish a foundation for future research and development in the design of eco-friendly materials for next-generation applications.