The doctrine of natural justice is one of the foundational pillars of administrative and constitutional law, representing the moral conscience of the legal system. It embodies the principles of fairness, equity, and justice that guide judicial and quasi-judicial proceedings. Originating from the ancient common law of England and evolving through centuries of jurisprudence, the doctrine serves as a safeguard against arbitrary exercise of power by administrative or judicial authorities. In India, natural justice has gained constitutional recognition through Articles 14 and 21 of the Constitution, ensuring that every individual is treated fairly and without prejudice. This paper examines the concept, origin, scope, and application of natural justice, emphasizing its principles—audi alteram partem (hear the other side) and nemo judex in causa sua (no one shall be a judge in his own cause). It further explores the doctrine’s judicial interpretation, relevance in administrative law, exceptions, and its evolving role in the age of modern governance and artificial intelligence.