Juvenile idiopathic arthritis (JIA) is the most prevalent chronic rheumatic disease in children, marked by persistent arthritis lasting over 6 weeks in individuals under 16 years of age. This chapter provides a comprehensive review of JIA, highlighting its complex etiology, classification, diverse subtypes, and clinical features. It also discusses diagnostic criteria, epidemiology, pathogenesis, clinical presentation, extra-articular manifestations, differential diagnosis, and management strategies. Advances in biologic agents, digital health, artificial intelligence, and personalized medicine have significantly improved disease outcomes and are discussed. It also underscores the importance of early diagnosis, regular monitoring, and individualized therapy to improve prognosis and reduce complications in children with JIA.