Al-Qaeda (Arabic: القاعدة, “the base”) is a transnational Islamist terrorist organization founded by Osama bin Laden, Abdullah Azzam, and others in the late 1980s, initially in the context of the Soviet-Afghan War. It operates on a decentralized network model and adheres to a jihadist-Salafist ideology, holding that armed struggle against what it characterizes as apostate Muslim governments and Western powers - particularly the United States and Israel - is a religious obligation. Al-Qaeda is designated a terrorist organization by the United Nations, the United States, the European Union, and most member states of the international community.

Al-Qaeda emerged from the Maktab al-Khidamat (“Services Office”), a network established during the 1980s to recruit and funnel fighters and funding into the Afghan resistance against Soviet occupation. Following the Soviet withdrawal in 1989, bin Laden and his associates reoriented the organization toward a broader global jihad. Al-Qaeda established training camps and operational infrastructure in Sudan during the early 1990s, then returned to Afghanistan under Taliban protection after 1996. The organization's structure combines a hierarchical leadership core with a franchise and affiliate model, enabling semi-autonomous cells and regional branches - including al-Qaeda in the Arabian Peninsula (AQAP), al-Qaeda in the Islamic Maghreb (AQIM), and al-Shabaab - to operate with varying degrees of independence. See Al-Qaeda - History for a full account.

Al-Qaeda is responsible for the September 11, 2001, attacks on the United States, in which 19 operatives hijacked four commercial aircraft, crashing two into the World Trade Center in New York City, one into the Pentagon in Arlington, Virginia, and one into a field near Shanksville, Pennsylvania, killing approximately 2,977 people. The attacks precipitated the U.S.-led invasion of Afghanistan in October 2001, the dismantling of al-Qaeda's Afghan sanctuary, and a sustained global counterterrorism campaign. Osama bin Laden was killed by U.S. special operations forces in Abbottabad, Pakistan, on 2 May 2011. Leadership passed to Ayman al-Zawahiri, who was killed in a U.S. drone strike in Kabul on 31 July 2022. Al-Qaeda's core organizational capacity has been substantially degraded since 2001, though its affiliates remain active across multiple regions.

Al-Qaeda's ideology draws on the writings of Sayyid Qutb, Ibn Taymiyya, and other Islamist thinkers to justify armed jihad against governments it deems insufficiently Islamic and against Western states it holds responsible for the subjugation of Muslim peoples. It rejects secular nationalism, democracy, and Western liberalism as incompatible with Islamic governance. The organization targets civilians deliberately, a practice it justifies theologically on the grounds that citizens of democratic states bear collective responsibility for their governments' policies. Scholars of political Islam disagree about the degree to which al-Qaeda's ideology represents a mainstream or fringe interpretation of Islamic jurisprudence; see Al-Qaeda - Islamic Jurisprudence Debate and Al-Qaeda and Mainstream Islam - Viewpoint.

Al-Qaeda's relationship with the Afghan Taliban is one of longstanding but at times uneasy alliance. The Taliban provided sanctuary prior to 2001 and, per United Nations monitoring reports, maintained ties with al-Qaeda after retaking Afghanistan in 2021, despite pledging otherwise in the 2020 Doha Agreement. Al-Qaeda and the Islamic State of Iraq and Syria (ISIS, also known as ISIL or Daesh) were formally affiliated until 2014, when ISIS declared an independent caliphate and a rupture occurred. The two organizations have since competed for recruits, territory, and ideological authority, and have at times engaged in direct conflict.

There is broad consensus among governments and international bodies on al-Qaeda's designation as a terrorist organization responsible for mass-casualty attacks. See Al-Qaeda - Counterterrorism Consensus for an overview of areas of agreement and their limits.

• Western counterterrorism framework - Al-Qaeda is a non-state actor conducting unlawful warfare against civilian and military targets; military, intelligence, and law-enforcement responses are legitimate and necessary. Viewpoint: Counterterrorism Framework
• Blowback and root-causes analysis - Al-Qaeda's emergence and appeal are substantially products of U.S. and Western foreign policy, including support for authoritarian Arab regimes and intervention in Muslim-majority countries; addressing grievances is necessary for durable reduction of the threat. Viewpoint: Blowback and Root Causes
• Islamist jihadist framing - Proponents of this view within the organization and its sympathizers hold that al-Qaeda's campaign is a legitimate defensive jihad. This viewpoint is described here for encyclopedic completeness; it is not endorsed by this site. Viewpoint: Jihadist Framing
• Civil liberties critique of the “War on Terror” - Post-9/11 counterterrorism measures, including surveillance expansion, detention without trial, and targeted killing programs, have undermined civil liberties and rule of law disproportionate to the threat posed. Viewpoint: Civil Liberties Critique

• Al-Qaeda - History
• Al-Qaeda - Debate
• Al-Qaeda - Counterterrorism Consensus
• September 11 Attacks
• War on Terror
• Taliban
• Islamic State (ISIS)
• Islamism
• Jihadism

1. National Commission on Terrorist Attacks Upon the United States. The 9/11 Commission Report. Washington, D.C.: U.S. Government Printing Office, 2004.
2. Burke, Jason. Al-Qaeda: The True Story of Radical Islam. London: I.B. Tauris, 2003.
3. Gerges, Fawaz A. The Far Enemy: Why Jihad Went Global. Cambridge: Cambridge University Press, 2005.
4. United Nations Security Council. “Twenty-ninth report of the Analytical Support and Sanctions Monitoring Team.” S/2024/92. February 2024.
5. Bergen, Peter L. The Longest War: The Enduring Conflict Between America and Al-Qaeda. New York: Free Press, 2011.
6. Wright, Lawrence. The Looming Tower: Al-Qaeda and the Road to 9/11. New York: Knopf, 2006.