This chapter examines odontogenic/primary pain, focusing on its etiology, pathophysiology, clinical presentation, and diagnostic considerations. It reviews pain arising from the dental pulp, periodontal structures, and periapical tissues, distinguishing between reversible and irreversible pulpitis, acute and chronic apical periodontitis, and other related conditions. Emphasis is placed on thorough history taking, clinical examination, and appropriate use of diagnostic tests to guide effective treatment planning. This chapter also discusses pain referral patterns, differential diagnosis, and the importance of recognizing non-odontogenic sources to avoid mismanagement and improve patient outcomes.