Public Interest Litigation (PIL) has emerged as a distinctive judicial mechanism in India, enabling courts to address systemic environmental harms beyond the constraints of traditional adversarial litigation. Since the 1980s, the Supreme Court of India (SCI) and various High Courts (HC) have employed PIL to expand access to environmental justice, interpret constitutional rights expansively, and influence environmental governance. This paper examines the role of PIL as an instrument of environmental governance in India through a constitutional and judicial lens. It analyses how courts have utilized PIL to operationalize Articles 21, 48A, and 51A(g) of the Constitution, develop environmental principles such as sustainable development and the precautionary principle, and shape regulatory enforcement. Adopting a doctrinal and case-based empirical methodology, the study examines landmark environmental PILs and evaluates judicial remedies, monitoring mechanisms, and compliance outcomes. The paper argues that while PIL has significantly strengthened environmental governance by addressing regulatory gaps and executive inaction, it has also raised concerns relating to institutional capacity, democratic accountability, and separation of powers. The study concludes that PIL remains a transformative but contested tool of environmental governance, requiring calibrated judicial intervention and stronger institutional coordination to ensure long-term environmental protection