Polyethylene terephthalate (PET), a thermoplastic polymer, has emerged as a cornerstone in artificial ligament development due to its unique chemical structure, exceptional tensile strength, and biocompatibility. Its applications span diverse medical fields, particularly in orthopedics and spinal surgeries, such as anterior cruciate ligament (ACL) reconstruction and acromioclavicular (AC) joint repair. Recent innovations, including the SHLee ligament, have demonstrated PET’s ability to overcome challenges in spinal stabilization. Despite its advantages, PET has limitations, including susceptibility to infection, which has led to the exploration of polypropylene-based alternatives. This chapter delves into PET’s chemical properties, medical applications, and future prospects in artificial ligament development.