Gastric acid secretion is a physiological process by which the stomach produces hydrochloric acid (HCl) to aid in digestion and provide protection against ingested pathogens. Acid is secreted by parietal cells of the gastric glands through the H⁺/K⁺-ATPase (proton pump). The process is regulated by three major stimulatory mediators—acetylcholine, histamine, and gastrin—and inhibited by factors such as prostaglandins and somatostatin. Understanding gastric acid secretion is essential in pharmacology, as it forms the basis for the therapeutic use of antacids, H₂-receptor blockers, and proton pump inhibitors in acid-related disorders.