This chapter explores the chemical foundations and sustainable attributes of animal-derived fibers, focusing on wool and silk. Wool, derived from the fleece of various mammals, offers remarkable insulation, moisture management, and resilience due to its keratin structure. Silk, produced by silkworms, is prized for its strength, luster, and smooth texture, resulting from its fibroin composition. Both fibers exemplify sustainable alternatives to synthetic textiles, aligning with the growing demand for eco-friendly materials. The chapter delves into their properties, production processes, and applications, highlighting the innovative approaches to enhance their sustainability and functionality in the modern textile industry.