Heart rate variability (HRV) has emerged as a vital tool reflecting autonomic nervous system (ANS) regulation and its disruption in psychosomatic and clinical conditions. This comprehensive review synthesizes recent research on HRV, emphasizing its application in psychosomatic disorders. HRV components such as high-frequency (HF) power indicate parasympathetic activity, whereas low-frequency (LF) power reflects combined sympathetic and parasympathetic influences. Stress and psychosomatic disorders including anxiety, depression, chronic pain, fibromyalgia, and insomnia are consistently associated with reduced HRV, characterized by diminished vagal tone and altered LF/HF ratios. These changes underscore autonomic imbalance and heightened sympathetic dominance. HRV indices such as standard deviation normal to normal, root mean square of successive difference, and HF are reliable markers of autonomic function, yet methodological heterogeneity and lack of standardization remain challenges. HRV’s predictive value extends to cardiovascular disease risk, cognitive impairment, and mortality, emphasizing its role in preventive health. In clinical practice, HRV monitoring aids in assessing autonomic dysregulation, guiding biofeedback, relaxation therapies, and personalized interventions. Future directions include enhancing wearable device accuracy, integrating artificial intelligence for real-time analysis, and developing standardized guidelines for HRV use in psychosomatic disorder management. Overall, HRV offers a noninvasive, versatile tool for assessing autonomic health, stress, and psychosomatic conditions, with significant potential to enhance healthcare strategies globally. © 2025 Heart and Mind.