The lungs and kidneys are vital organs that work together to maintain homeostasis, the stable internal environment required for normal cellular function. Although the primary role of the lungs is gas exchange, their function is closely connected with kidney regulation. One of the most important interactions between the lungs and kidneys involves acid–base balance. During cellular metabolism, carbon dioxide (CO₂) is produced and transported through the blood to the lungs, where it is eliminated during exhalation. This respiratory removal of CO₂ is essential for maintaining normal blood pH. The kidneys provide the complementary long-term mechanism by regulating bicarbonate (HCO₃⁻) levels and excreting hydrogen ions. Oxygen availability is another important factor. Kidney tissue requires an adequate oxygen supply to support filtration, tubular transport, reabsorption, and other metabolic processes. Conditions that impair pulmonary gas exchange and cause hypoxemia may therefore affect renal function. Similarly, excessive retention of CO₂ can produce respiratory acidosis, increasing the need for renal compensation through changes in bicarbonate handling and hydrogen-ion excretion. The lungs and kidneys are also connected through mechanisms involved in blood pressure, fluid, and electrolyte regulation. Changes in oxygenation and vascular function may influence pathways associated with renal regulation, including the renin–angiotensin–aldosterone system (RAAS). This system plays an important role in controlling blood pressure and maintaining sodium and water balance. Chronic respiratory disorders may place additional physiological stress on the kidneys, particularly when they are associated with persistent hypoxemia, carbon dioxide retention, or acid–base disturbances. Therefore, normal lung function is important for maintaining the conditions required for efficient renal activity. In conclusion, the lungs and kidneys function as an interconnected physiological system. The lungs regulate carbon dioxide and oxygen levels, while the kidneys provide long-term regulation of electrolytes and acid–base status. Maintaining healthy respiratory function therefore contributes to the preservation of normal kidney function and overall internal balance. Al-Mustaqbal University The First University in Iraq