Syria conducts an air strike on Khan Shaykhun using chemical weapons, killing 89 civilians.

The Khan Shaykhun chemical attack took place on 4 April 2017 on the town of Khan Shaykhun in the Idlib Governorate of Syria. The town was reported to have been struck by an airstrike by government forces followed by massive civilian chemical poisoning. The release of a toxic gas, which included sarin, or a similar substance, killed at least 89 people and injured more than 541, according to the opposition Idlib Health Directorate. The attack was the deadliest use of chemical weapons in the Syrian civil war since the Ghouta chemical attack in 2013.

Khan Shaykhun is a town in the Maarrat al-Nu'man District, within the southern Idlib Governorate of northwestern Syria.

Syria's chemical weapons program began in the 1970s with weapons and training from Egypt and the Soviet Union, with production of chemical weapons in Syria beginning in the mid-1980s. For some time, Syria was believed to have the world's third-largest stockpile of chemical weapons, after the United States and Russia. Prior to September 2013 Syria had not publicly admitted to possessing chemical weapons, although Western intelligence services believed it to hold one of the world's largest stockpiles. In September 2013, French intelligence put the Syrian stockpile at 1,000 tonnes, including Yperite, VX and "several hundred tonnes of sarin". At the time, Syria was one of a handful of states which had not ratified the Chemical Weapons Convention. In September 2013, Syria joined the CWC, and agreed to the destruction of its weapons, to be supervised by the Organisation for the Prohibition of Chemical Weapons (OPCW), as required by the convention. A joint OPCW-United Nations mission was established to oversee the destruction process. Syria joined OPCW after international condemnation of the August 2013 Ghouta chemical attack, for which Western states held the Syrian government responsible and agreed to the prompt destruction of its chemical weapons.