US 10th Mountain Division soldiers in Afghanistan

U.S. Soldiers boarding a Boeing CH-47 Chinook helicopter during Operation Anaconda in Afghanistan

The War on Terror (also known as the Global War on Terror or the War on Terrorism) is the campaign launched by the United States of America, under the Presidency of George W. Bush, with the support of the United Kingdom, NATO and other countries. The campaign was launched in response to the September 11, 2001 attacks and had the stated objective of eliminating international terrorism.

The phrase War on Terror was used frequently by former US President George W. Bush and other high-ranking US officials to denote a global military, political, legal and ideological struggle against organizations designated as terrorist and regimes that were accused of having a connection to them or providing them with support or were perceived or presented as posing a threat to the US and its allies in general. It was typically used with a particular focus on militant Islamists and al-Qaeda.

The administration of President Barack Obama has discontinued use of the term "War on Terror" and instead uses the term "Overseas Contingency Operation". However, President Obama has stated that the U.S. is at war with al-Qaeda.

Both the term and the policies it denotes have been a source of ongoing controversy, as critics argue it has been used to justify unilateral preventive war, human rights abuses and other violations of international law.