Al-Qaeda (; Arabic: القاعدة, romanized: al-Qāʿidah, lit. 'the Base', IPA: [alˈqaː.ʕi.da]) is a pan-Islamist militant organization led by Sunni Jihadists who self-identify as a vanguard spearheading a global Islamist revolution to unite the Muslim world under a supra-national Islamic caliphate. Its membership is mostly composed of Arabs, but also includes people from other ethnic groups. Al-Qaeda has mounted attacks on civilian, economic and military targets of the US and its allies; such as the 1998 US embassy bombings, the USS Cole bombing and the September 11 attacks. The organization is designated as a terrorist group by NATO, the UN Security Council, the European Union, and various countries around the world.

The organization was founded in a series of meetings held in Peshawar during 1988, attended by Abdullah Azzam, Osama bin Laden, Muhammad Atef, Ayman al-Zawahiri and other veterans of the Soviet–Afghan War. Building upon the networks of Maktab al-Khidamat, the founding members decided to create an organization named "Al-Qaeda" to serve as a "vanguard" for jihad. When Saddam Hussein invaded and occupied Kuwait in 1990, bin Laden offered to support Saudi Arabia by sending his Mujahideen fighters. His offer was rebuffed by the Saudi government, which instead sought the aid of the United States. The stationing of U.S. troops in the Arabian Peninsula prompted bin Laden to declare a jihad against both the rulers of Saudi Arabia - whom he denounced as murtadd (apostates) - and against the US. From 1992, al-Qaeda established its headquarters in Sudan until it was expelled in 1996. It then shifted its base to the Taliban-ruled Afghanistan and later expanded to other parts of the world, primarily in the Middle East and South Asia.