Many natural fibers are lightweight and display remarkable strength and toughness. These properties originate from the fibers' hierarchical structures, assembled from the molecular to macroscopic scale. The natural spinning systems that produce such fibers are highly energy efficient, inspiring researchers to mimic these processes to realize robust artificial spinning. Significant developments have been achieved in recent years toward the preparation of high-performance bio-based fibers. Beyond excellent mechanical properties, bio-based fibers can be functionalized with a series of new features, thus expanding their sophisticated applications in smart textiles, electronic sensors, and biomedical engineering. Here, recent progress in the construction of bio-based fibers is outlined. Various bioinspired spinning methods, strengthening strategies for mechanically strong fibers, and the diverse applications of these fibers are discussed. Moreover, challenges in reproducing the mechanical performance of natural systems and understanding their dynamic spinning process are presented. Finally, a perspective on the development of biological fibers is given.