Dehydration is a common cause of illness and death among children in developing countries, claiming over 2 million lives annually. It results from an imbalance where fluid loss exceeds intake. Common causes in children include diarrhea, vomiting, and fever. Clinical features include decreased skin turgor, sunken eyes/fontanel, dry mucous membranes, and reduced urine output. Treatment depends on severity but involves oral rehydration with solutions like Pedialyte for mild cases and intravenous fluids for moderate to severe dehydration to restore electrolyte and volume deficits. Proper management can prevent complications and save lives.