Murder–suicide in the context of "Mayerling incident"

A suicide attack (also known by a wide variety of other names, see below) is a deliberate attack in which the perpetrators intentionally end their own lives as part of the attack. These attacks are a form of murder–suicide that is often associated with terrorism or war. When the attackers are labelled as terrorists, the attacks are sometimes referred to as an act of suicide terrorism. Military use of suicide is not directly regulated by international law, but suicide attacks sometimes violate prohibitions against perfidy or targeting civilians. Suicide attacks have occurred in various contexts, ranging from military campaigns—such as the Japanese kamikaze pilots during World War II (1944–1945)—to more contemporary Islamic terrorist campaigns—including the September 11 attacks in 2001. Suicide attacks have been used by a wide range of political ideologies, from far-right (Japan and Germany in WWII) to far-left (such as the PKK and JRA).

The September 11 attacks were the deadliest terrorist attacks in human history, causing the deaths of 2,996 people, including 19 hijackers who committed murder–suicide and 2,977 victims. Thousands more were injured, and long-term health effects have arisen as a consequence of the attacks. New York City took the brunt of the death toll when the Twin Towers of the World Trade Center complex in Lower Manhattan were attacked, with an estimated 1,700 victims from the North Tower and around a thousand from the South Tower. 200 mi (320 km) southwest in Arlington County, Virginia, another 125 were killed in the Pentagon. The remaining 265 fatalities included the 92 passengers and crew of American Airlines Flight 11, the 65 aboard United Airlines Flight 175, the 64 aboard American Airlines Flight 77 and the 44 aboard United Airlines Flight 93. The attack on the World Trade Center's North Tower alone made the September 11 attacks the deadliest act of terrorism in human history.

Most of those who perished were civilians, except for: 344 members of the New York City Fire Department and New York Fire Patrol; 71 law enforcement officers who died in the World Trade Center and on the ground in New York City; 55 military personnel who died at the Pentagon in Arlington County, Virginia; a U.S. Fish and Wildlife Service officer who died when Flight 93 crashed into a field near Shanksville, Pennsylvania; and the 19 terrorists who died on board the four aircraft. At least 102 countries lost citizens in the attacks.