The Center for Strategic and International Studies (CSIS) is an American think tank based in Washington, D.C. From its founding in 1962 until 1987, it was an affiliate of Georgetown University, initially named the Center for Strategic and International Studies of Georgetown University. The center conducts policy studies and strategic analyses of political, economic and security issues throughout the world, with a focus on issues concerning international relations, trade, technology, finance, energy and geostrategy.

A think tank, or policy institute, is a research institute that performs research and advocacy concerning topics such as social policy, political strategy, economics, military, technology, and culture. Most think tanks are non-governmental organizations, but some are semi-autonomous agencies within government, and some are associated with particular political parties, businesses or the military. Think tanks are often funded by individual donations, with many also accepting government grants.