Al-Qaeda, alternatively spelled al-Qaida and sometimes al-Qa'ida, (Arabic: القاعدة‎; al-qāʿidah; translation: The Base) is an Islamist group founded sometime between August 1988 and late 1989/early 1990. It operates as a network comprising both a multinational, stateless arm and a fundamentalist Sunni movement calling for al-qaeda al-sulbah (a vanguard of the strong).

Al-Qaeda has attacked civilian and military targets in various countries, the most notable being the September 11 attacks in 2001. These actions were followed by the US government launching the War on Terrorism. As of 2009, the group is believed to have between 200 and 300 members.

Characteristic techniques include suicide attacks and simultaneous bombings of different targets. Activities ascribed to it may involve members of the movement, who have taken a pledge of loyalty to Osama bin Laden, or the much more numerous "al-Qaeda-linked" individuals who have undergone training in one of its camps in Afghanistan or Sudan but not taken any pledge.