Organization for Security and Cooperation in Europe (OSCE), international organization established as the Conference on Security and Cooperation in Europe (CSCE) in 1973, during the cold war, to promote East-West cooperation. Headquarters are in Prague, Czech Republic. The CSCE's 1975 meeting in Helsinki, Finland, ratified the acts commonly known as the Helsinki Accords, which were signed by every European nation (except Albania, which did so later) and the United States and Canada. The OSCE is responsible for reviewing the implementation of those accords. Since the end of the cold war, it has also aimed to foster peace, prosperity, and justice in Europe. There are now 56 OSCE members, including all European nations, all former republics of the Soviet Union, and the United States and Canada.

The Helsinki Accords held the post-World War II European border arrangements to be permanent, and the signers agreed to respect the human rights and civic freedoms of their citizens, as well as to undertake various forms of international cooperation. Although the nonbinding accords did not have treaty status, they were the first international agreement signed by the Soviet Union to mention the rights of free speech and travel. The human-rights provisions had a significant role in galvanizing Soviet and other Eastern European dissidents in the late 1970s, who organized committees to monitor compliance with the Helsinki Accords. Subsequent conferences have been held in various European cities. At the 1990 Paris summit, leaders of the member nations signed a declaration respecting the territorial integrity of Europe, an act that signaled the end of the cold war; limitations were also placed on the size of conventional forces in Europe. An additional agreement in 1992 and a revised treaty in 1999 placed further limitations on conventional forces.