The autonomic nervous system is fundamental for maintaining cardiovascular homeostasis by integrating sympathetic and parasympathetic activity across central and peripheral circuits. Disruption of this finely tuned regulation, known as autonomic dysfunction, has emerged as a critical determinant of cardiovascular risk. Mechanistically, autonomic imbalance is characterized by reduced vagal activity, impaired baroreflex sensitivity, and heightened sympathetic drive, all of which contribute to hemodynamic instability, arrhythmogenesis, and adverse clinical outcomes. Baroreflex sensitivity and heart rate variability have been identified as independent predictors of mortality in post-myocardial infarction patients and individuals with chronic heart failure, providing incremental prognostic value beyond left ventricular function and conventional risk factors. Moreover, systemic diseases such as diabetes mellitus can precipitate cardiovascular autonomic neuropathy, a complication associated with silent myocardial ischemia, arrhythmias, and increased mortality. Wearable sensors and artificial intelligence-based analytic platforms enable continuous and non-invasive monitoring of autonomic function, facilitating earlier detection of subclinical abnormalities and supporting the integration of autonomic indices into prognostic models. Beyond conventional heart rate variability, advanced autonomic markers such as deceleration capacity and heart rate turbulence, supported by guideline-endorsed testing strategies and digital monitoring tools, provide incremental prognostic value. These advances represent a major step toward personalized cardiovascular medicine, in which autonomic dysfunction can serve not only as a mechanistic explanation of disease but also as a therapeutic and preventive target. Recognition of its mechanistic, diagnostic, and prognostic implications is essential for developing innovative strategies to reduce cardiovascular morbidity and mortality.