The September 11, 2001 attacks were carried out by the extremist group al‑Qaeda, led at the time by Osama bin Laden.

Who was responsible?

Most mainstream investigations and governments conclude that:

  • The overall responsibility lay with al‑Qaeda , an Islamist extremist organization that planned, financed, and coordinated the attacks.
  • Osama bin Laden is widely described as the mastermind and top leader who authorized and oversaw the operation.
  • Khalid Sheikh Mohammed is identified as the main operational planner who proposed the idea of using hijacked planes and worked out the details of the plot.
  • A group of 19 hijackers, most of them from Saudi Arabia and other Arab countries, physically hijacked four commercial airliners and turned them into weapons.

In official accounts, U.S. and U.K. authorities concluded soon after the attacks that al‑Qaeda, under bin Laden, was solely responsible for organizing and directing the plot.

How do we know?

Several kinds of evidence are cited in official and historical accounts:

  • Intelligence and investigative work quickly linked the 19 hijackers to al‑Qaeda networks and prior extremist activity.
  • Senior al‑Qaeda figures, including Osama bin Laden and Khalid Sheikh Mohammed, later made statements taking or describing responsibility for the attacks, including in videos and interrogations.
  • Government investigations, like those referenced by major encyclopedias and news organizations, have consistently described al‑Qaeda as the organizer of the attacks.

For example, reputable reference works note that bin Laden was considered the mastermind, with Khalid Sheikh Mohammed as the operational planner, backed by al‑Qaeda’s funding, training, and logistics.

Other claims and debates

There are many online discussions, especially on forums, that question or speculate about:

  • Whether any states indirectly supported or enabled parts of the operation.
  • Alternative theories about who “really” planned 9/11.

However, these views are not supported by the broad body of official investigations and expert historical work, which consistently attribute responsibility to al‑Qaeda under Osama bin Laden’s leadership.

Information gathered from public forums or data available on the internet and portrayed here.