Background: Chronic rhinosinusitis (CRS) and obstructive sleep apnea (OSA) frequently coexist, sharing inflammatory and anatomical pathways consistent with the "United Airway" This review examines the synergistic dysfunction linking these conditions. Methods: We conducted a comprehensive review synthesizing literature on the epidemiology, pathophysiology—including cytokine cascades and microbiome dysbiosis—and therapeutic outcomes of surgical and medical interventions for comorbid CRS and OSA. Results: Large-scale datasets confirm CRS as an independent risk factor for OSA. Pathophysiologically, the disorders are linked by mechanical obstruction, systemic cytokine spillover (IL-6, TNF-a), and nasopharyngeal microbiome dysbiosis (e.g., S. aureus biofilms). Therapeutically, Endoscopic Sinus Surgery (ESS) significantly improves subjective sleep quality (SNOT-22) and reduces CPAP pressure requirements, although it yields only trivial reductions in the Apnea-Hypopnea Index (AHI). Biologics like Dupilumab demonstrate rapid efficacy in improving sleep domains for CRS with nasal polyps. Conclusion: CRS and OSA are inextricably linked via mechanical and inflammatory mechanisms. A holistic "United Airway" management approach—optimizing nasal patency to facilitate CPAP adherence and reduce systemic inflammatory burden—is critical for improving patient outcomes.