This chapter comprehensively elaborates on the epidemiology, etiology, pathophysiology, clinical manifestations, diagnosis, differential diagnosis, treatments, and complications of ossification of spinal ligaments (OSL). Among the various types of OSL, ossification of the posterior longitudinal ligament and ossification of the ligamentum flavum are the most common, with incidence rates varying across ethnic groups and geographical regions. Regarding etiology, genetics, endocrine and metabolic factors, mechanical stress and trauma, as well as inflammation and immune responses, are all considered contributors to the development of OSL. Depending on the location of ligament ossification, patients present with a diverse range of clinical manifestations, including balance disorders, impaired motor function, and compression symptoms of the spinal cord and nerve roots. The diagnosis of OSL primarily relies on imaging examinations such as X-rays, computed tomography, and magnetic resonance imaging. Surgery is the primary treatment modality, and specific surgical approaches need to be selected based on the patient’s condition and the surgeon’s expertise. With the continuous innovation of new surgical techniques and imaging technologies, novel treatment methods are continually developing. Overall, the present chapter emphasizes the complexity and therapeutic challenges of OSL, providing comprehensive medical guidance for understanding and managing this condition.