Seven Sisters

The Seven Sisters were seven major Western oil companies that controlled much of the international petroleum industry from the 1940s through the 1970s.

Standard Oil: A major American oil trust founded by John D. Rockefeller and dissolved by court order in 1911. Its breakup produced companies that later joined the Seven Sisters.
Oil concession: A contract granting a company rights to explore for and produce petroleum in a defined territory. Concessions secured the Sisters' long-term access to major oil-producing regions.
Calouste Gulbenkian: An Armenian businessman and oil intermediary who negotiated petroleum deals across the Ottoman Empire and Europe. His brokerage helped assemble the Iraq Petroleum Company, which included several Sisters.
OPEC: An intergovernmental organization founded in 1960 to coordinate the petroleum policies of oil-exporting countries. It gave producer states a collective forum to contest the Sisters' influence.
Oil nationalization: The transfer of oil resources or petroleum operations from private ownership to state control. Nationalization dismantled the concessionary control on which the Sisters' power rested.
Anglo-Persian Oil Company: A British oil company founded to develop petroleum resources in Persia, later renamed BP. It became one of the seven companies through its Persian concession and global expansion.
Vertical integration: Business ownership or control of multiple successive stages in producing and selling a good. The companies linked extraction, transport, refining, and marketing under common control.
Winston Churchill: British prime minister during the Second World War and again from 1951 to 1955. As First Lord of the Admiralty, he backed British government investment in the Anglo-Persian Oil Company.
Nationalization of the Iranian oil industry: Iran's 1951 transfer of the Anglo-Iranian Oil Company's assets and operations to state control. It directly confronted a Sister's concession and triggered an international oil crisis.
1973 oil crisis: A sharp rise in oil prices and supply disruption following an Arab oil embargo in 1973. The crisis demonstrated producers' growing ability to use oil supply as political leverage.

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