The pleura is a thin mesothelial membrane composed of two continuous layers that envelop the lungs and line the inner chest wall. The visceral pleura is firmly adherent to the lung parenchyma, following its contours, including the interlobar fissures, while the parietal pleura lines the inner surface of the thoracic cavity. These two layers converge at the hilum of the lung, where the pleural reflections meet. The potential space between the layers—the pleural space—contains a thin film of lubricating fluid produced and absorbed primarily by the parietal pleura. This fluid minimizes friction between the lungs and the chest wall during respiration and maintains the slightly negative intrapleural pressure, which is essential for alveolar expansion during inspiration. Histologically, the two pleural layers differ in structure, reflecting their distinct physiologic roles. Moreover, their vascular, lymphatic, and neural supplies are anatomically and functionally distinct, which has important implications for pleural and pulmonary pathophysiology. This chapter provides a detailed overview of the anatomy, histology, physiology, and pleural fluid dynamics that together form the foundation for understanding pleural disease.