Roman law gave rise to Res Judicata, which is now a part of all legal systems worldwide. According to the res judicata doctrine, the parties are often prohibited from bringing up the same issue or claiming again in later proceedings once a definitive decision has been rendered. Res Judicata's origins can be attributed to the demand for judicial effectiveness and eliminating needless litigation. It acts as a key supporter of the legal system, encouraging the efficient use of judicial tools and hastening the settlement of legal issues. Res judicata offers certainty and predictability in case of outcomes while also assisting in avoiding the strain and expense of several judicial actions. This research paper aims to comprehensively analyze res judicata and its applications in the Indian legal system. It explores the origins of res judicata, its elements and requirements, and its significance in different legal jurisdictions. The paper also explores the exceptions and limitations to res judicata and analyses the potential challenges and criticisms associated with its application. Through an in-depth examination of case laws, this research paper contributes to a better understanding of the doctrine of res judicata and its implications for the administration of justice.