Refeeding syndrome is a potentially fatal metabolic complication that arises during the nutritional rehabilitation of severely malnourished individuals. This chapter reviews the pathophysiology of refeeding syndrome, highlighting the hallmark biochemical disturbances such as hypophosphatemia, hypokalemia, hypomagnesemia, thiamine deficiency, and fluid overload. It outlines the mechanisms underlying these imbalances and their clinical consequences, including cardiovascular, neurological, and respiratory dysfunction. Diagnostic criteria, including recent classifications by the American Society for Parenteral and Enteral Nutrition (ASPEN), are discussed along with key risk factors and screening tools. The chapter emphasizes prevention through early risk assessment, careful electrolyte correction, thiamine supplementation, and gradual reintroduction of nutrition. Guidelines for safe refeeding and individualized management strategies are also reviewed, underscoring the importance of multidisciplinary care in reducing morbidity and mortality associated with refeeding syndrome.