This review synthesizes current evidence on autonomic nervous system (ANS) dysfunction in irritable bowel syndrome (IBS). Patients with IBS often exhibit sympathovagal imbalance–reduced vagal tone with relative sympathetic hyperactivity–which correlates with symptom severity and shows subtype specificity. The ANS orchestrates bidirectional brain–gut communication via interactions with psychosocial factors, low-grade neuroinflammation, and the gut microbiota. Key mechanisms include vagal afferent