The reign of King Le Thanh Tong (1460–1497) marked a defining stage in the formation of Vietnam’s centralized monarchy, combining political stability with legal and cultural development. His philosophy of governance, grounded in humanism, synthesized Confucian ethics and indigenous Vietnamese values to create an enduring model of moral governance. Based on historical and philosophical analysis of royal decrees, the Hong Duc Code, and annalistic records, this study clarifies how Le Thanh Tong integrated moral virtue with legal order to ensure that justice was guided by compassion and humanity. The research focuses on his conception of the ruler and the people, the ethical foundation of administration, and the moral role of education and literature in statecraft. The findings reveal that his synthesis of virtue and law transformed the state into an instrument of ethical education, where law served morality and morality legitimized law. His humanistic philosophy shaped the evolution of Vietnamese legal and political thought and continues to offer theoretical and moral significance for building a socialist rule-of-law state centered on humanity, justice, and responsibility.