The Organization of the Petroleum Exporting Countries (OPEC) comprises countries that have organized for the purpose of negotiating with oil companies on matters of petroleum production, prices, and future concession rights. The members, which constitute a cartel, agree on the quantity and the prices of the oil exported.
The OPEC headquarters is situated in Vienna, Austria. OPEC seeks to regulate oil production, and thereby manage oil prices, in a coordinated effort among the member countries, especially through setting quotas for its members. Member countries hold about 75% of the world's oil reserves, and supply about 40% of the world's oil.