A SWAT (Special Weapons and Tactics) team is a generic term for a police tactical unit within the United States, though the term has also been used by other nations.

SWAT units are generally trained, equipped, and deployed to resolve "high-risk situations", often those regular police units are not trained or equipped to handle, such as shootouts, standoffs, raids, hostage-takings, and terrorism. SWAT units are equipped with specialized weapons and equipment not normally issued to regular police units, such as automatic firearms, high-caliber sniper rifles, stun grenades, body armor, ballistic shields, night-vision devices, and armored vehicles, among others. SWAT units are often trained in special tactics such as close-quarters combat, door breaching, crisis negotiation, and de-escalation.

The first SWAT units were formed in the 1960s to handle riot control and violent confrontations with criminals. The number and usage of SWAT units increased in the 1980s during the War on Drugs and the 1990s following incidents such as the North Hollywood shootout and Columbine High School massacre, with further increases in the 2000s for counterterrorism interests in the aftermath of the September 11 attacks. In the United States by 2005, SWAT teams were deployed 50,000 times every year, almost 80% of the time to serve search warrants, most often for narcotics. By 2015, the number of annual SWAT deployments had increased to nearly 80,000 times a year. Despite their heightened involvement in high-risk scenarios, research on their use of force has shown varied results. A study by professor Jimmy J. Williams and professor David Westall found that there wasn't a significant difference in the frequency of use of force between SWAT and non-SWAT officers when responding to similar situations.

The United States National Tactical Officers Association's definition of SWAT is:

SWAT: A designated law enforcement team whose members are recruited, selected, trained, equipped and assigned to resolve critical incidents involving a threat to public safety which would otherwise exceed the capabilities of traditional law enforcement first responders and/or investigative units.

According to the Historical Dictionary of Law Enforcement, the term "SWAT" was used as an acronym for the "Special Weapons and Tactics" established as a 100-man specialized unit in 1964 by the Philadelphia Police Department in response to an alarming increase in bank robberies. The purpose of this unit was to react quickly and decisively to bank robberies while they were in progress, using a large number of specially trained officers who had a great amount of firepower at their disposal. The tactic worked and was used to resolve other types of incidents involving heavily armed criminals. The Los Angeles Police Department (LAPD) Special Weapons and Tactics was established in 1967. LAPD inspector Daryl Gates envisioned the "SWAT" acronym to be "Special Weapons Attack Team" but this was not accepted by deputy chief Edward M. Davis who instead approved Special Weapons and Tactics.

The LAPD promoted what became known as SWAT teams for a variety of reasons. After the racially-charged Watts riots in Los Angeles in August 1965, the LAPD began considering tactics it could use when faced with urban unrest, rioting, or widespread violence. Daryl Gates, who led the LAPD response to the riots, would later write that police at the time did not face a single mob, but rather "people attacking from all directions". New York University professor Christian Parenti has written that SWAT teams were originally conceived of as an "urban counterinsurgency bulwark".

Another reason for the creation of SWAT teams was the fear of lone or barricaded gunmen who might outperform police in a shootout, as happened in Austin with Charles Whitman.