This review summarizes the current neurobiological evidence on the relationship between heart rate variability (HRV) and psychological stress. HRV, which reflects the variation in the time intervals between heartbeats, is a reliable indicator of autonomic nervous system (ANS) activity and can be used to assess psychological stress and mental health. The sympathetic nervous system (SNS) is hyperactivated during chronic stress, leading to physiological and psychological abnormalities. HRV is influenced by parasympathetic activity, with low parasympathetic activity characterized by reduced high-frequency (HF) and increased low-frequency (LF) components. Neuroimaging studies suggest that HRV may be linked to cortical regions involved in stress appraisal, such as the ventromedial prefrontal cortex. HRV is a noninvasive method to measure ANS function and can be used in various clinical situations, including psychological stress evaluations. Studies have shown that HRV variables change in response to stress induced by various methods. The most frequently reported factor associated with HRV variation is low parasympathetic activity. HRV can be used as a tool to assess stress and mental health, but it is important to consider the patient's medical and psychological history when interpreting HRV results. HRV is sensitive to changes in ANS activity and can reflect physiological changes associated with stress. However, HRV is influenced by various factors, including physiological, lifestyle, and environmental factors, which can affect its interpretation. The review highlights the importance of HRV as a stress indicator and its potential clinical applications in assessing psychological stress and mental health.This review summarizes the current neurobiological evidence on the relationship between heart rate variability (HRV) and psychological stress. HRV, which reflects the variation in the time intervals between heartbeats, is a reliable indicator of autonomic nervous system (ANS) activity and can be used to assess psychological stress and mental health. The sympathetic nervous system (SNS) is hyperactivated during chronic stress, leading to physiological and psychological abnormalities. HRV is influenced by parasympathetic activity, with low parasympathetic activity characterized by reduced high-frequency (HF) and increased low-frequency (LF) components. Neuroimaging studies suggest that HRV may be linked to cortical regions involved in stress appraisal, such as the ventromedial prefrontal cortex. HRV is a noninvasive method to measure ANS function and can be used in various clinical situations, including psychological stress evaluations. Studies have shown that HRV variables change in response to stress induced by various methods. The most frequently reported factor associated with HRV variation is low parasympathetic activity. HRV can be used as a tool to assess stress and mental health, but it is important to consider the patient's medical and psychological history when interpreting HRV results. HRV is sensitive to changes in ANS activity and can reflect physiological changes associated with stress. However, HRV is influenced by various factors, including physiological, lifestyle, and environmental factors, which can affect its interpretation. The review highlights the importance of HRV as a stress indicator and its potential clinical applications in assessing psychological stress and mental health.