The USA PATRIOT Act (commonly known as the Patriot Act) was a landmark Act of the United States Congress, signed into law by President George W. Bush. The formal name of the statute is the Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism (USA PATRIOT) Act of 2001, and the commonly used short name is a contrived acronym that is embedded in the name set forth in the statute.The Patriot Act was enacted following the September 11 attacks and the 2001 anthrax attacks with the stated goal of dramatically tightening U.S. national security, particularly as it related to foreign terrorism. In general, the act included three main provisions:

expanded surveillance abilities of law enforcement, including by tapping domestic and international phones;

easier interagency communication to allow federal agencies to more effectively use all available resources in counterterrorism efforts; and

increased penalties for terrorism crimes and an expanded list of activities which would qualify for terrorism charges.The law is controversial due to its authorization of indefinite detention without trial of immigrants, and due to the permission given to law enforcement to search property and records without a warrant, consent, or knowledge. (Though generally, they need a warrant or consent to conduct the search.) Since its passage, several legal challenges have been brought against the act, and federal courts have ruled that a number of provisions are unconstitutional.

It contains many sunset provisions beginning December 31, 2005, approximately four years after its passage. Before the sunset date, an extension was passed for four years which kept most of the law intact. In May 2011, President Barack Obama signed the PATRIOT Sunset Extensions Act of 2011, which extended three provisions. These provisions were modified and extended until 2019 by the USA Freedom Act, passed in 2015. In 2020, efforts to extend the provisions were not passed by the House of Representatives, and as such, the law has expired.