This chapter provides an in-depth exploration of coir fibers, focusing on their production, properties, and diverse applications. Derived from the mature husks of coconut trees, coir fibers are known for their resiliency, resistance to weather, durability, high lignin content, and environmental sustainability. The chapter emphasizes two distinct varieties of coconut trees, highlighting the unique attributes of the fibers they produce. The extraction and processing methods, including traditional and modern techniques, are detailed to illustrate their impact on fiber quality and performance. A comprehensive analysis of the physical, mechanical, thermal, and sound absorption properties of coir fibers is presented, including tensile strength, thermal stability, and surface morphology. The chapter also delves into the effects of chemical modifications, which enhance the fibers’ characteristics and expand their utility in industrial applications. Applications in construction, textiles, and eco-friendly materials are discussed, demonstrating the potential of coir fibers as a renewable and sustainable resource. This chapter serves as a valuable resource for understanding the fundamental aspects of coir fibers and their role in advancing sustainable material innovations.