Abstract: This chapter sets out the problematic nature of non-governmental organisations (NGOs), pointing to the strict application of the term to business actors, but noting also that it in common parlance it is usually confined to social, human rights and environment groups (and that this volume adopts this position). It notes that NGOs have entrenched their place in global governance in two major ways: by providing services of value to international NGOs (IGOs) by lobbying national governments to support international policy measures and by reporting on a state's non-compliance. The importance of issue and arena characteristics for influencing NGO influence are noted; but so too is the fact that, while NGOs are generally regarded as having a positive influence on global governance, they are not without their negative aspects. The key roles of NGOs in agenda-setting, global policy formulation and policy implementation are then discussed.