Functional endoscopic sinus surgery (FESS) is a minimally invasive technique widely adopted since the 1980s for managing sinonasal conditions such as chronic rhinosinusitis and nasal polyposis. This article presents a detailed cadaveric video guide to FESS, illustrating the step-by-step dissection of the maxillary, ethmoid, and sphenoid sinuses. Emphasis is placed on anatomical landmarks, surgical technique, and complication avoidance. Intended primarily for residents and early-career practitioners, the guide aims to enhance surgical proficiency, promote standardized practice, and ultimately improve patient outcomes in sinonasal surgery.