In times of economic and financial crises, climate change and environmental pollution, pandemic dangers, and numerous other problems of global reach, policy makers at the local, regional, national, and global levels need profound knowledge to make the right decisions to help shape a sustainable future. Because think tanks provide reliable and relevant information on different domestic and international issues and give advice about what can be done in the face of contemporary and future challenges, they have increasingly gained influence on public policy worldwide. A growing number of increasingly specialized think tanks address emerging challenges with their research activities. This entry discusses the concept and history of think tanks, the competences of these organizations, and the role they play in the policy process.