This chapter assesses the third element of corporate social responsibility (CSR) applicable to multinational enterprises (MNEs): environmental sustainability. MNEs are active in industries that contribute not only to global heating but also, among other things, to environmental pollution, the production of toxic waste, the reduction of biodiversity, and the depletion of natural resources. In addition, traditional approaches to corporate governance and financial accounting focus narrowly on corporate profitability, externalizing the costs of environmental impacts to the wider community. On the other hand, MNEs are also the main repositories of modern, environmentally friendly, technology and expertise on environmentally sound management practices. Equally, new approaches that internalize environmental factors into corporate costs, decision making, and reporting are slowly emerging. Accordingly, the chapter considers not only the prevention of environmental harm arising from MNE activities, but also how MNEs might be encouraged to use the best technologies and managerial practices to enhance environmentally sustainable economic and social development. It outlines the core concepts informing the environmental responsibilities of MNEs and looks at the debate over MNE impacts—both positive and negative—on the environment, before focusing on the environmental regulation of MNEs.