Utilitarianism, a consequentialist ethical theory primarily developed by Jeremy Bentham and John Stuart Mill, has profoundly influenced law and ethics over the past two centuries. Its focus on maximizing happiness or utility continues to shape legal frameworks and ethical decision making in various contexts, from public policy to individual rights. This paper examines the historical development of utilitarianism, tracing its impact on legal reforms, particularly in criminal justice, and its role in shaping contemporary ethical discourse. Through an analysis of Bentham's and Mill's contributions, the paper explores how utilitarian principles have been applied in both jurisprudence and broader societal ethics, assessing their enduring relevance in modern legal systems.