Serangan 11 September
Sebahagian daripada terrorism in the United States
Barisan teratas: The Twin Towers of the Pusat Dagangan Dunia membakar 2nd row, left to right: Collapsed section of Pentagon; Penerbangan 175 crashes into 2 WTC; 3rd row, left to right: A firefighter requests bantuan di World Trade Center site; Ground Zero; An engine dari Penerbangan 93 is recovered Barisan bawah: Penerbangan 77's collision with the Pentagon as captured by three berturut-turut CCTV bingkai
Lokasi	New York City, U.S.; Arlington County, Virginia, U.S.; Stonycreek Township berhampiran Shanksville, Pennsylvania, AS
Tarikh	September 11, 2001; 17 tahun yang lalu 8:46 a.m. \u2013 10:28 a.m. (EDT)
Sasaran	Pusat Dagangan Dunia (AA 11 and UA 175) Pentagon (AA 77) White House or Capitol AS (UA 93; failed)
Jenis serangan	Aircraft hijackings Suicide attacks Pembunuhan beramai-ramai keganasan
kematian	2,996 (2,977 victims + 19 hijackers)
Kecederaan tidak membawa maut	6,000 +
Penjenayah	Al-Qaeda[1] (Lihat juga tanggungjawaband perampas)
Tiada. daripada peserta	19

. Serangan 11 September (juga dirujuk sebagai 9/11)^[a] were a series of four coordinated serangan pengganas oleh Islamic terrorist kumpulan al-Qaeda^[2][3][4] against the United States on the morning of Tuesday, September 11, 2001. The attacks killed 2,996 people, injured over 6,000 others, and caused at least $10 billion in infrastructure and property damage.^[5][6]Additional people died of 9/11-related cancer and penyakit pernafasan in the months and years following the attacks.

Four passenger pesawat udara operated by two major U.S. passenger pengangkut udara (United Airlines and American Airlines)\u2014all of which departed from airports in the northeastern part of the United States terikat untuk California\u2014were dirampas by 19 al-Qaeda terrorists. Two of the planes, American Airlines Flight 11and Penerbangan United Airlines 175, were crashed into the North and South towers, respectively, of the Pusat Dagangan Dunia kompleks di Manhattan Rendah. Within an hour and 42 minutes, both 110-story towers collapsed. Debris and the resulting fires caused a partial or complete collapse of all other buildings in the World Trade Center complex, including the 47-story 7 World Trade Centre tower, as well as significant damage to ten other large surrounding structures. A third plane, American Airlines Flight 77, was crashed into Pentagon (the headquarters of the Jabatan Pertahanan Amerika Syarikat) dalam Arlington County, Virginia, which led to a partial collapse of the building's west side. The fourth plane, Penerbangan United Airlines 93, was initially flown toward Washington, D.C., but crashed into a field in Stonycreek Township berhampiran Shanksville, Pennsylvania, after its passengers thwarted the hijackers. 9/11 is the single deadliest incident for firefighters and pegawai penguatkuasa undang-undang^[7] dalam history of the United States, with 343 and 72 killed, respectively.

Suspicion quickly fell on al-Qaeda. The United States responded by launching the Peperangan menentang keganasan and menyerang Afghanistan to depose the Taliban, which had failed to comply with U.S. demands to extradite Osama bin Laden and expel al-Qaeda from Afghanistan. Many countries strengthened their anti-terrorism legislation and expanded the powers of penguatkuasaan undang-undang and agensi perisikan to prevent terrorist attacks. Although al-Qaeda's leader, Osama bin Laden, initially denied any involvement, in 2004 he claimed responsibility for the attacks.^[1] Al-Qaeda and bin Laden cited U.S. support of Israel, kehadiran U.S. troops in Saudi Arabia, dan sanctions against Iraq as motives. After evading capture for almost a decade, Osama bin Laden was located and killed in Pakistan by Pasukan Enam SEAL daripada Tentera Laut Amerika Syarikat Mei 2011.

The destruction of the World Trade Center and nearby infrastructure seriously harmed the economy of Manhattan Rendah and had a significant effect on global markets, which resulted in the closing of Wall Street until September 17 and the civilian airspace in the U.S. and Canada until September 13. Many closings, evacuations, and cancellations followed, out of respect or fear of further attacks. Cleanup of the World Trade Center site was completed in May 2002, and the Pentagon was repaired within a year. On November 18, 2006, pembinaan of One World Trade Centre began at the World Trade Center site. The building was officially opened on November 3, 2014.^[8][9] pelbagai peringatan have been constructed, including the Peringatan & Muzium Nasional 11 September di New York City, the Pentagon Memorial in Arlington County, Virginia, and the Peringatan Nasional Penerbangan 93 in a field in Stonycreek Township near Shanksville, Pennsylvania.