Background: Obstructive sleep apnea (OSA) is a prevalent sleep-related breathing disorder associated with multiple systemic comorbidities. Gastroesophageal reflux disease (GERD) has been frequently reported among patients with OSA; however, the magnitude of this association remains uncertain. Objective: To systematically evaluate and quantify the association between obstructive sleep apnea and gastroesophageal reflux disease in adult populations. Methods: A systematic review and meta-analysis were conducted in accordance with PRISMA guidelines and a protocol registered in PROSPERO (CRD420261278563). Electronic searches were performed in PubMed/MEDLINE, Scopus, Web of Science, and Embase. Observational studies assessing the association between OSA and GERD were included. Risk of bias was assessed using the Newcastle–Ottawa Scale. A random-effects meta-analysis was performed to pool odds ratios (ORs) with 95% confidence intervals (CIs). Results: Six observational studies were included in the quantitative synthesis. The pooled analysis demonstrated a statistically significant association between obstructive sleep apnea and gastroesophageal reflux disease, with a combined OR of 1.96. Moderate heterogeneity was observed among studies (I² = 65%). No substantial evidence of publication bias was identified based on funnel plot assessment. Conclusions: These findings suggest that obstructive sleep apnea is associated with nearly two-fold increased odds of gastroesophageal reflux disease and support increased clinical awareness rather than formal screening recommendations.