In 2010, the United Nations Environment Programme (UNEP) commissioned the Global Outlook on Gas Hydrates as part of its mandate to examine the environmental aspect of key emerging issues and provide accurate and objective scientific assessments for the benefit of the science community and policy makers. This report, written by experts in the field, provides a review of the science and history of this emerging energy source, evaluates the current state of research and explores the potential impacts of gas hydrates on the future global energy mix. By commissioning this report, UNEP neither encourages nor promotes the development and use of gas hydrates as an energy source.