The organ in the body primarily responsible for breathing is the lungs. These vital organs play a crucial role in the respiratory system, facilitating gas exchange between the body and the environment. The lungs are spongy, air-filled structures located in the thoracic cavity, where they expand and contract to allow inhalation and exhalation. During inhalation, oxygen is drawn into the lungs, while carbon dioxide is expelled during exhalation. The lungs work closely with the diaphragm, intercostal muscles, and respiratory pathways to maintain efficient breathing, which is essential for supplying oxygen to the body and removing waste gases.