Myxedema coma is a rare but life-threatening complication of severe, often long-standing untreated hypothyroidism. It occurs when adaptive mechanisms—such as peripheral vasoconstriction and reduced blood volume—begin to fail. These adaptations can be overwhelmed by precipitating events such as infections or cold exposure, pushing the patient into a critical state requiring immediate intensive care. Early recognition and intervention are crucial, as mortality rates range from 20% to 60% even with advanced ICU support. This chapter provides a detailed, stepwise approach to managing myxedema coma in the ICU, covering initial recognition, diagnostic steps, critical care interventions, hormone replacement therapy, and strategies for addressing precipitating factors [1, 2]. [Ref: Algorithm 51.1].