Jacobson’s Progressive Muscular Relaxation (PMR), developed by Edmund Jacobson in the 1920s, is a structured relaxation technique based on the principle that mental calmness arises from physical relaxation. It involves systematically tensing and then releasing different muscle groups, helping individuals become aware of and reduce bodily tension associated with stress and anxiety. By modulating sympathetic arousal and promoting parasympathetic activity, PMR lowers heart rate, blood pressure, and muscle tone, fostering a state of deep relaxation. Clinically, it is effective in anxiety disorders, insomnia, hypertension, and chronic pain, and is frequently integrated into cognitive-behavioral and mindfulness-based therapies. Simple, inexpensive, and evidence-based, PMR remains a cornerstone of relaxation training in modern psychiatric and psychosomatic practice.