In the United States, terrorism is defined as the systematic or threatened use of violence in order to create a climate of fear with the goal of intimidating a population or government and thereby spurring political, religious, or ideological change. This article serves as a list and a compilation of acts of terrorism, attempts to commit acts of terrorism, and other such items which pertain to terrorist activities which are engaged in by non-state actors or spies who are acting in the interests of state actors or persons who are acting without the approval of foreign governments within the domestic borders of the United States.

During the American Civil War, pro-Confederate Bushwhackers and pro-Union Jayhawkers in Missouri and Kansas respectively engaged in cross border raids, committed acts of violence against civilians and soldiers, stole goods, and burned farms down. The most infamous event was the 1863 Lawrence Massacre in Lawrence, Kansas, on August 21, 1863, when around 150 people were killed by Quantrill's Raiders because of the town's anti-slavery sentiment. Other acts of terrorism which occurred during the war included the 1863 Chesapeake Affair and the 1864 St. Albans Raid, the former being committed by British subjects.

Since the end of the Civil War, organized groups or lone wolf white supremacists have committed many acts of domestic terrorism against African Americans. This form of terrorism has consisted of expulsions, lynchings, hate crimes, shootings, bombings and other acts of violence. Such acts of violence overwhelmingly occurred in the Southern United States, and they included acts of violence which were committed by the Ku Klux Klan (KKK).McVeigh, Rory. "Structural Incentives for Conservative Mobilization: Power Devaluation and the Rise of the Ku Klux Klan, 1915–1925". Social Forces, Vol. 77, No. 4 (June 1999), p. 1463. Acts of white supremacist terrorism include the Wilmington massacre of 1898, the East St. Louis massacre of 1917, the Elaine massacre of 1919, the Ocoee massacre of 1920, the Tulsa race massacre of 1921, and the Rosewood massacre of 1923.

A 2017 report by the U.S. Government Accountability Office found that out of the 85 deadly extremist incidents which had occurred since the September 11 attacks (9/11) in 2001, white supremacist groups were responsible for 73%, while radical Islamist extremists were responsible for 27%. The total number of deaths caused by each group was about the same. However, 41% of the deaths that were attributable to radical Islamists all occurred in a single event: the 2016 Orlando nightclub shooting in which 49 people were killed. No deaths were attributed to left-wing groups. The Department of Homeland Security reported in 2020 that white supremacists posed the top domestic terrorism threat, which FBI director Christopher Wray confirmed in 2021, noting that the bureau had elevated the threat to the same level as ISIS.Multiple sources:

Totals in the U.S.

+Terrorist incidents in the United StatesNational Consortium for the Study of Terrorism and Responses to Terrorism. (2018). Global Terrorism Database (globalterrorismdb_0718dist.xlsx ). Retrieved from https://www.start.umd.edu/gtd University of MarylandNational Consortium for the Study of Terrorism and Responses to Terrorism. (2018). Global Terrorism Database (gtd1993_0718dist.xlsx ). Retrieved from https://www.start.umd.edu/gtd University of Maryland Year Number ofincidents Deaths Injuries2017659593220166468139201538545820142926192013202343620122077201110022010174172009111841200818213200780020066114200521002004900200333002002334112001413,00816,5152000320719995320401998314319974021819963521191995601787381994551016199336101,0051992322319913024199032571989423141988271119873411198649136198540313198463378019834485198278113719817481519806715221979691858197887881977130417197610544119751492415819749416541973584533197268103519712472055197046833160 Total 2,8723,78121,707

A 2017 report by The Nation Institute and the Center for Investigative Reporting analyzed a list of the terrorist incidents which occurred in the US between 2008 and 2016. It found: 115 far-right inspired terrorist incidents. 35% of these incidents were foiled (this number means that no terrorist attacks occurred) and 29% of them resulted in fatalities. These incidents caused 79 deaths. 63 Islamist inspired terrorist incidents. 76% of these terrorist incidents were foiled (this number means that no terrorist attacks occurred) and 13% of them resulted in fatalities. These incidents caused 90 deaths. 19 far-left inspired terrorist incidents. 20% of these terrorist incidents were foiled (this number means that no terrorist attacks occurred) and 10% of them resulted in fatalities. Two of these incidents were described as "plausibly" attributed to a perpetrator with left-wing sympathies and caused 7 deaths. These are not included in the official government database.

According to a report which is based on Justice Department figures which were released by the U.S. government in January 2018, about three out of four people who were convicted on charges of international terrorism between September 11, 2001, to December 31, 2016, were foreign-born. According to the Justice Department, 549 people were convicted on charges of international terrorism, including 254 people who were citizens of other countries, 148 people were naturalized citizens and 148 people were natural-born-citizens. In a speech made before a joint session of Congress on February 28, 2017, President Donald Trump incorrectly attributed these findings to domestic terrorism; in actuality, the findings were based on cases in which international terrorists may have been brought to the United States for prosecution.

In 2015, the Triangle Center on Terrorism and Homeland Security and the Police Executive Research Forum conducted a nationwide survey of 382 police and sheriff departments. Nearly 74% of respondents stated that anti-government violence was their top concern with regard to threats from violent extremists, while about 39% of respondents stated that "Al Qaeda-inspired" violence was their top concern."Law Enforcement Assessment of the Violent Extremism Threat" — https://sites.duke.edu/tcths/files/2013/06/Kurzman_Schanzer_Law_Enforcement_Assessment_of_the_Violent_Extremist_Threat_final.pdf

In the 2010s, the national conversation on terrorism largely focused on Islamic extremist acts, however, law enforcement groups made it clear that Muslim extremists perpetrate a minute percentage of the ideologically based terrorist attacks which are perpetrated in the United States. Since November 9, 2001, only about 9 American Muslims per year have taken part in terrorist plots in the United States, in total, 20 incidents resulted in about 50 deaths. A 2012 study showed that in about the same time period right-wing extremists were responsible for about 337 attacks per year, in total, they killed more than 5 times the number of people killed by Muslims in the United States.

The National Consortium for the Study of Terrorism and Responses to Terrorism maintains Profiles of Individual Radicalization in the United States, a database which contains over 1,800 profiles of individuals who have been radicalized by ideologies since 1948. The database shows that from 1948 through 2016, 40.0% of identified extremists were far-right, 24.5% of identified extremists were Islamist and 17.4% of identified extremists were far-left, while 18.2% of identified extremists were "single issue" individuals.

In May 2019 and for the first time in its history, the FBI identified fringe conspiracy theories as a potential source of domestic terrorism, it specifically cited QAnon.

A June 2020 study of domestic terrorist incidents by the Center for Strategic and International Studies (CSIS) reported that during the previous 25 years, the majority of attacks and plots were perpetrated and hatched by far-right attackers. This trend has accelerated in recent years, with this sector being responsible for about 66% of all of the attacks and plots which were perpetrated in 2019, and it was also responsible for 90% of all of those attacks which were perpetrated in 2020. The next most potentially dangerous group has been "religious extremists", the majority "Salafi jihadists inspired by the Islamic State and al-Qaeda", while the number planned by the far left has reduced to a minute fraction since the mid-2000s.

In October 2020, the Department of Homeland Security released the Homeland Threat Assessment, a report detailing various domestic threats to US national security. It states that, out of all domestic terror attacks resulting in lethal threats to life between 2018 and 2019, "WSEs [white supremacist extremists] conducted half of all lethal attacks (8 of 16), resulting in the majority of deaths (39 of 48)".

Soon after the assassination of Charlie Kirk, U.S. President Trump claimed that "the radicals on the left are the problem" with political violence. Opinion editors, as well as both far-right commentators and Trump critics, have compared Charlie Kirk's killing to the Reichstag fire—the 1933 arson of the German parliament building that Hitler used as a pretext to suspend civil liberties and prosecute political opposition—some calling Kirk's killing Trump's "Reichstag fire moment". How Democracies Die author, professor Steven Levitsky, said that exploiting Charlie Kirk's killing to justify unleashing attacks on critics is "page one of the authoritarian playbook".

Attacks by type Anti-abortion violence

Since 1997, there have been 8 murders, 17 attempted murders, 42 bombings, and 186 arson attacks aimed at abortion clinics and multiple providers across the US. In some cases small groups of clinics have been attacked multiple times. 1991: The Central Ohio Women's Clinic that was housed in a building owned by the Planned Parenthood of Central Ohio in Columbus, Ohio was burned by members of the Christian Liberation Army, with damages estimates $75,000 in damages. Nine days later threw a firebomb into the Capital Care Women's Center in Columbus, Ohio, leaving damages sustained $250,000 in damages. 1993: Dr. David Gunn was murdered by anti-abortion extremist and Christian fundamentalist, Michael F. Griffin. 1994: Abortion provider Dr. John Britton and James Barrett (both murdered) and his wife June (shot but survived) became victims of Reverend Paul Jennings Hill. 1996–1998: Anti-abortion extremist Eric Rudolph cited biblical passages as his motivation for a series of bombings, including Atlanta's Olympic Centennial Park, a lesbian bar, and several abortion clinics. Rudolph acknowledges his attacks were religiously motivated, but denies that his brief association with the racist Christian Identity movement was a motivation for his attacks. 1996: Dr. Calvin Jackson of New Orleans, Louisiana was stabbed 15 times, losing 4 pints of blood. Donald Cooper was charged with second degree attempted murder and was sentenced to 20 years. "Donald Cooper's Day of Violence", by Kara Lowentheil, Choice! Magazine, December 21, 2004 1998: Anti-abortion extremist James Kopp murdered Dr. Barnett Slepian and went on a series of anti-abortion shooting sprees, both in the U.S. and Canada. 2006: David McMenemy of Rochester Hills, Michigan, crashed his car into the Edgerton Women's Care Center in Davenport, Iowa. He then doused the lobby in gasoline and started a fire. McMenemy committed these acts in the belief that the center was performing abortions; however, Edgerton is not an abortion clinic. Time magazine listed the incident in a "Top 10 Inept Terrorist Plots" list. 2009: Anti-abortion extremist Scott Roeder murdered Dr. George Tiller in Kansas. 2015: Robert Lewis Dear killed three people in a shooting at a Planned Parenthood clinic in Colorado Springs, Colorado. At his court hearings Dear declared himself a "warrior for the babies".

Antisemitism