This comprehensive review article explores the sustainability of fiber-reinforced polymer composites (FRCs) made from renewable and biodegradable natural fibers and sustainable polymer resins. The article highlights the environmental benefits and challenges of these composites, particularly in high-performance engineering applications where synthetic fiber composites like glass or carbon FRCs dominate. It discusses the importance of balancing composite performance and biodegradability to achieve environmentally conscious materials. The review covers various aspects, including the sustainability considerations at different stages of the composite development process—materials, performance, applications, and end-of-life. It also details the types of sustainable natural fibers and polymer resins, and presents current achievements in the mechanical and functional properties of these composites. The article further surveys their potential applications across diverse engineering fields, emphasizing the shift towards more sustainable materials due to environmental regulations, socioeconomic awareness, and the diminishing availability of fossil fuels. The review concludes by discussing the advantages and drawbacks of biocomposites and natural-fiber-reinforced composites, highlighting their renewability, environmental friendliness, and cost-effectiveness, while acknowledging the need for further research to address potential chemical release concerns.This comprehensive review article explores the sustainability of fiber-reinforced polymer composites (FRCs) made from renewable and biodegradable natural fibers and sustainable polymer resins. The article highlights the environmental benefits and challenges of these composites, particularly in high-performance engineering applications where synthetic fiber composites like glass or carbon FRCs dominate. It discusses the importance of balancing composite performance and biodegradability to achieve environmentally conscious materials. The review covers various aspects, including the sustainability considerations at different stages of the composite development process—materials, performance, applications, and end-of-life. It also details the types of sustainable natural fibers and polymer resins, and presents current achievements in the mechanical and functional properties of these composites. The article further surveys their potential applications across diverse engineering fields, emphasizing the shift towards more sustainable materials due to environmental regulations, socioeconomic awareness, and the diminishing availability of fossil fuels. The review concludes by discussing the advantages and drawbacks of biocomposites and natural-fiber-reinforced composites, highlighting their renewability, environmental friendliness, and cost-effectiveness, while acknowledging the need for further research to address potential chemical release concerns.