The Islamic State (IS), also known as the Islamic State of Iraq and the Levant (ISIL), the Islamic State of Iraq and Syria (ISIS) and Daesh, is a transnational Salafi jihadist militant organisation and unrecognised quasi-state. ISIL occupied significant territory in Iraq and Syria in 2013, but lost most of it in 2017 and 2019. In 2014, the group proclaimed itself to be a worldwide caliphate, and claimed religious and political authority over all Muslims worldwide, a claim not accepted by the vast majority of Muslims. It is designated as a terrorist organisation by the United Nations and many countries around the world, including Muslim countries.

By the end of 2015, its self-declared caliphate ruled an area with a population of about 12 million, where they enforced their extremist interpretation of Islamic law, managed an annual budget exceeding US$1 billion, and commanded more than 30,000 fighters. After a grinding conflict with American, Iraqi, and Kurdish forces, IS lost control of all its Middle Eastern territories by 2019, subsequently reverting to insurgency from remote hideouts while continuing its propaganda efforts. These efforts have garnered a significant following in northern and Sahelian Africa, where IS still controls a significant territory. Originating in the Jaish al-Ta'ifa al-Mansurah founded by Abu Omar al-Baghdadi in 2004, the organisation (primarily under the Islamic State of Iraq name) affiliated itself with al-Qaeda in Iraq and fought alongside them during the 2003–2006 phase of the Iraqi insurgency. The group later changed their name to Islamic State of Iraq and Levant for about a year, before declaring itself to be a worldwide caliphate, called simply the Islamic State (الدولة الإسلامية, ad-Dawlah al-Islāmiyya).

During its rule in Syria and Iraq, the group "became notorious for its brutality".