Large-scale hydropower projects have recently become one of the most controversial topics regarding the sustainability of green energy. Projects like the Belo Monte or the Ilisu Dam have been widely criticized for infringing human rights and damaging nature. Nevertheless, hydropower remains an attractive energy source and provides for approximately 20% of electricity worldwide. This book explores the sustainability debate in the hydropower community based on the multi-stakeholder initiative called "Hydropower Sustainability Assessment Protocol" launched by the International Hydropower Association and analysis the role of international law in regulating the activities of transnational corporations in this area.