Stability studies play a vital role in the pharmaceutical industry by ensuring the safety, quality, purity, and effectiveness of drug products throughout their shelf life. This review highlights the importance of stability testing in determining suitable storage conditions, expiration dates, and product performance under different environmental conditions. Various factors affecting stability, including temperature, humidity, light, oxygen, pH, and excipients, are discussed along with different types of stability such as chemical, physical, microbiological, therapeutic, and photostability. The review also summarizes major regulatory guidelines provided by ICH, WHO, USFDA, and CDSCO for global harmonization of stability studies. Different testing methods, including accelerated, real-time, cyclic stress, and retained sample testing, are explained. Additionally, the role of packaging systems and smart technologies in maintaining pharmaceutical stability and ensuring patient safety is emphasized.