This chapter details the role of magnetic resonance imaging (MRI) in diagnosing temporomandibular joint (TMJ) disorders and diseases, emphasizing its superiority in evaluating both hard and soft tissue structures, particularly the fibrocartilaginous disc. It reviews TMJ anatomy, imaging protocols, and the interpretation of normal and pathological findings, including disc displacement, internal derangements, joint effusion, degenerative joint disease, and inflammatory arthritides such as rheumatoid arthritis and juvenile idiopathic arthritis. MRI’s ability to assess disc morphology, joint space changes, and inflammatory processes in open and closed mouth positions is highlighted, supporting accurate diagnosis and management strategies.