Business has a central role in international environmental law. Both treaties and treatises regard private economic actors as secondary players, and see states as the overwhelmingly dominant targets and prescribers of environmental law. This article examines the roles and goals of business entities with respect to international environmental law. It then considers how international law has accommodated the place of business in environmental policy with respect to two key issues: corporations as the target of legal obligations; and corporations as participants in the process of international environmental law, particularly with respect to law making and implementation. The article also looks at business-initiated non-governmental organisations, both those composed of, or representing, businesses within one state, as well as those with a more international profile. It examines business and environmental regulation, focusing on two visions of international business. Finally, the article analyses business as the target of international environmental law duties, civil liability conventions, soft regulation, corporations as prescribers of norms, monitoring and enforcement of business behaviour, and litigation.