Endonasal surgery is a surgical methodology performed entirely or primarily through the nasal passages. As a research field and clinical concept, it investigates the techniques, outcomes, indications, and limitations of procedures targeting the nasal cavity, paranasal sinuses, and adjacent anatomical structures including the skull base and orbit. Characterized by its minimally invasive approach and reliance on specialized endoscopic visualization, this domain focuses on advancing therapeutic strategies to manage diverse pathologies in these complex regions while minimizing patient morbidity and optimizing recovery.