The textile industry uses large quantities of fibers obtained from various animals, of which wool obtained from sheep is commercially the most important. Unlike vegetable fibers such as cotton, wool fiber has some technical problems that affect the quality and performance of the finished product such as felting shrinkage, handle, luster, pilling, and dyeability. As a result, different methods are used for modifying wool fibers in order to achieve good finishing results. Chemical methods such as oxidation, reduction, and enzyme treatments have been used to solve the technical problems to a certain extent. However, chemical treatments result in pollution-related problems as some chemicals are retained in the fiber. Due to the effects of pollution caused by various chemical treatments, physical treatments such as plasma treatment, which are capable of imparting good surface modification effects comparable to chemical treatment, have been introduced. Since the 1960s, scientists have successfully used plasma treatment to improve surface properties of fibers. The fibers that can be modified by plasma include almost all kinds of fibers such as metallic fibers, glass fibers, carbon fibers, and organic fibers. Plasma-treated wool fibers have different physical and chemical properties compared with untreated wool fibers. These changes in properties alter the performance of the fiber during various textile processes such as spinning, dyeing, and finishing and help produce versatile wool products of superior quality. The aim of this entry is to critically examine the developments in plasma treatment of wool.