This special issue showcases recent developments in the design, processing, and application of sustainable composite materials for advanced and eco-friendly solutions. Innovative approaches in utilizing renewable, recycled, and waste-derived resources to produce functional composites with enhanced properties is the highlight. It includes contributions on material characterization, property optimization, non-destructive testing, and performance improvements through advanced processing techniques and smart design strategies. The role of machine learning and data-driven methods in material optimization, offering new insights into sustainable material development. By integrating traditional and emerging technologies, this issue aims to address current challenges in material sustainability and promote eco-conscious practices across diverse industries. The findings presented here reflect the importance of circular economy principles, resource efficiency, and green manufacturing concepts in the continuous evolution of high-performance composite materials for a wide range of modern applications.