This chapter examines the United Nations Environment Programme’s (UNEP) pivotal role in fostering peaceful change within global environmental governance over fifty years. UNEP’s inception at the Stockholm Conference, informed by scientific consensus and diplomatic foresight, marked a transformative approach to international collaboration for sustainability. This analysis employs a tridimensional framework – practical, political, and personal – to interrogate UNEP’s impact on environmental governance. It delves into the vision for UNEP at its foundational moment, its operational evolution, and its adaptive strategies in navigating the complex interplay of global power dynamics, from large powers to small states. The chapter highlights UNEP’s leadership in key environmental achievements, notably the reversal of ozone layer depletion and its emergent role in conflict resolution and peacebuilding. By focusing on UNEP’s trajectory and contributions, this narrative underscores the intricate ties between environmental protection and peace. The overarching theme emphasizes the necessity of continuous political mobilization and scientific engagement to address the urgent environmental crises of our time, echoing UNEP’s call for renewed, cooperative, and ecologically conscious global governance.

This chapter elaborates upon the latter part of the Stockholm Conference preparation period, including key Swedish science diplomacy interventions and the production of three landmark scientific reports on climate change, acid rain, and environmental monitoring. It also recounts the efforts of Maurice Strong and Barbara Ward to reconcile the emerging North–South divide ahead of Stockholm by organizing a meeting of development economists in Founex, Switzerland. The drafting of the Stockholm Declaration, as well as other aspects of the actual Conference, its parallel events, and its final outcomes, are examined. The chapter also explores other important early-1970s developments in Stockholm related to the Conference and the ongoing institutionalization of international climate science. These include the environmental turn at the Royal Swedish Academy of Sciences embodied by the launch of the journal Ambio in 1972, a large donation to the Academy by a Swedish industrialist that led to the establishment of the influential Beijer Institute, and the convening of another major GARP Conference in Stockholm in 1974.