The 1973 oil crisis or first oil crisis began in October 1973 when the members of the Organization of Arab Petroleum Exporting Countries (OAPEC), led by Saudi Arabia, proclaimed an oil embargo. The embargo was targeted at nations that had supported Israel during the Yom Kippur War. The initial nations targeted were Canada, Japan, the Netherlands, the United Kingdom and the United States, though the embargo also later extended to Portugal, Rhodesia and South Africa.

By the end of the embargo in March 1974, the price of oil had risen nearly 300%, from US$3 per barrel ($19/m3) to nearly $12 per barrel ($75/m3) globally; US prices were significantly higher. The embargo caused an oil crisis, or "shock", with many short- and long-term effects on global politics and the global economy. It was later called the "first oil shock", followed by the 1979 oil crisis, termed the "second oil shock".

The Organization of the Petroleum Exporting Countries (OPEC, OH-pek) is an intergovernmental organization of 13 countries. Founded on 14 September 1960 in Baghdad by the first five members (Iran, Iraq, Kuwait, Saudi Arabia, and Venezuela), it has since 1965 been headquartered in Vienna, Austria, although Austria is not an OPEC member state. As of September 2018, the 13 member countries accounted for an estimated 44 percent of global oil production and 81.5 percent of the world's "proven" oil reserves, giving OPEC a major influence on global oil prices that were previously determined by the so-called "Seven Sisters" grouping of multinational oil companies.

The stated mission of the organization is to "coordinate and unify the petroleum policies of its member countries and ensure the stabilization of oil markets, in order to secure an efficient, economic and regular supply of petroleum to consumers, a steady income to producers, and a fair return on capital for those investing in the petroleum industry." Economists often cite OPEC as a textbook example of a cartel that cooperates to reduce market competition, but one whose consultations are protected by the doctrine of state immunity under international law. The organization is also a significant provider of information about the international oil market.

The formation of OPEC marked a turning point toward national sovereignty over natural resources, and OPEC decisions have come to play a prominent role in the global oil market and international relations. The effect can be particularly strong when wars or civil disorders lead to extended interruptions in supply. In the 1970s, restrictions in oil production led to a dramatic rise in oil prices and in the revenue and wealth of OPEC, with long-lasting and far-reaching consequences for the global economy. In the 1980s, OPEC began setting production targets for its member nations; generally, when the targets are reduced, oil prices increase. This has occurred most recently from the organization's 2008 and 2016 decisions to trim oversupply.

Current OPEC members are Algeria, Angola, Equatorial Guinea, Gabon, Iran, Iraq, Kuwait, Libya, Nigeria, the Republic of the Congo, Saudi Arabia, the United Arab Emirates and Venezuela. Ecuador, Indonesia and Qatar are former OPEC members. A larger group called OPEC+ was formed in late 2016 to have more control on the global crude oil market.