This article provides a comprehensive overview of Functional Endoscopic Sinus Surgery (FESS) as a primary treatment for chronic rhinosinusitis (CRS) and its expanding role in managing various sinonasal and skull base pathologies. It explores the clinical significance of FESS, the indications, contraindications, and stepwise surgical techniques. Key insights into the anatomy, equipment requirements, and common complications, such as orbital and skull-base injuries, are discussed. The article emphasizes the importance of multidisciplinary collaboration with specialists, including neurosurgeons, oncologists, and ophthalmologists, as well as the essential role of postoperative care in preventing recurrence and improving patient outcomes. By combining advanced imaging, navigation, and careful surgical technique, FESS offers improved safety and efficacy for patients with CRS and related conditions.