The Ghouta chemical attack occurred during the Syrian Civil War in the early hours of 21 August 2013. Several opposition-controlled areas in the suburbs around Damascus, Syria, were struck by rockets containing the chemical agent sarin. Estimates of the death toll range from at least 281 people to 1,729. The attack was the deadliest use of chemical weapons since the Iran–Iraq War.
Inspectors from the United Nations Mission arrived in Syria on August 18, three days before the attack. They were present at the Syrian government's invitation to look into previous alleged chemical weapons use. The inspectors were staying in central Damascus, 12 kilometers or less from all three attack sites. The UN requested access to sites in Ghouta the day after the attack. Syrian government and rebel forces continued to clash in the area on 22 and 23 August, the Syrian military continued to shell Ghouta and the UN called for a ceasefire to allow inspectors to visit the Ghouta sites. The Syrian government granted the UN's request on 25 August. The inspectors visited and investigated at Moadamiyah in Western Ghouta on 26 August and at Zamalka and Ein Tarma in Eastern Ghouta on 28 and 29 August.
In mid-September 2013, the UN investigation team reported that it had confirmed the use of sarin in the Ghouta attack. The Mission "collected clear and convincing evidence that surface-to-surface rockets containing the nerve agent sarin were used in the Ein Tarma, Moadamiyah and Zalmalka in the Ghouta area of Damascus." In 2014, a report of the UN Human Rights Council found that "significant quantities of sarin were used in a well-planned indiscriminate attack targeting civilian-inhabited areas, causing mass casualties. The evidence available concerning the nature, quality and quantity of the agents used on 21 August indicated that the perpetrators likely had access to the chemical weapons stockpile of the Syrian military, as well as the expertise and equipment necessary to manipulate safely large amount of chemical agents." It also stated that the chemical agents used in the Khan al-Assal chemical attack "bore the same unique hallmarks" as those used in Al-Ghouta attack.
The Syrian government and opposition blamed each other for the attack. Many governments said the attack was carried out by forces of Syrian President Bashar al-Assad, a conclusion echoed by the Arab League and the European Union. The Russian government called the attack a false flag operation by the opposition to draw foreign powers into the civil war on the rebels' side. Åke Sellström, the leader of the UN Mission, has characterised attempts to say the rebels were responsible as unconvincing, resting in part upon "poor theories."
Several countries including France, the United Kingdom, the United States, debated whether to intervene militarily against government forces. On 6 September 2013, the United States Senate filed a bill to authorize use of military force against the Syrian military, mainly in response to the Ghouta attack. On 10 September 2013, the military intervention was averted when the Syrian government accepted a U.S.–Russian negotiated deal to turn over "every single bit" of its chemical weapons stockpiles for destruction and declared its intention to join the Chemical Weapons Convention.