Ethical business practices have moved from the periphery of corporate governance to its normative and strategic centre. This paper examines how corporate culture, integrity, and sustainability operate together as the “Unbreakable Trinity” of responsible business conduct and argues that long-term profitability cannot be separated from legality, accountability, stakeholder trust, and social legitimacy. The research problem addressed is the continuing gap between formal compliance and substantive ethical governance, particularly where corporations satisfy minimum legal duties while failing to internalise ethical decision-making across management, reporting, technology, environmental performance, and human-rights responsibilities. Adopting a doctrinal and analytical methodology, the paper evaluates international standards such as the United Nations Global Compact, the OECD Guidelines for Multinational Enterprises on Responsible Business Conduct, the UN Guiding Principles on Business and Human Rights, and the TRIPS framework, alongside Indian legal instruments including the Companies Act, 2013, SEBI’s Listing Obligations and Disclosure Requirements Regulations, CSR obligations, ESG disclosures, and business responsibility reporting. The study further draws upon comparative and Indian case studies, including Satyam, Enron, Volkswagen, Wells Fargo, Vedanta, and Tata Consultancy Services v. Cyrus Investments, to demonstrate how ethical failure produces legal sanctions, reputational harm, investor distrust, and institutional instability. The paper’s central finding is that corporate culture shapes behaviour, integrity directs behaviour, and sustainability preserves the legitimacy of business activity over time. It contributes to corporate law scholarship by presenting ethics not as a voluntary moral aspiration, but as a governance imperative that strengthens compliance, stakeholder confidence, digital accountability, environmental responsibility, and sustainable corporate competitiveness.