Foreign rebel fighters in the Syrian Civil War

During the course of the Syrian Civil War as well as the Iraqi Civil War (2014–present), many foreign nationals have fought in the conflict, some of whom have died. Fighters include those from the Gulf Arab states, Tunisia (following its own Tunisian revolution), Libya (following the similar Libyan Civil War), Bosnia, China, other Arab states, Russia's Chechnya and North Caucasus region, and Western countries. The conflict has taken on a largely sectarian bent with foreign Sunnis fighting for the Syrian opposition and the Islamic State of Iraq and the Levant (ISIL), while foreign Shias fight for the government. Estimates of the total number of foreign Sunnis who have fought for the rebels over the course of the conflict range from 5,000 to over 10,000, while foreign Shia fighters are thought to number around 10,000 at the most. Over 600 foreign fighters were killed in the first half of 2013 alone. The Soufan Group reported on 15 October 2016 that there has been "a significant increase in the number of foreign fighters travelling to Syria" since 2014. The U.S. State Department reported on 2 June 2016 that their "intelligence community" estimates that possibly "in excess of 40,000 total foreign fighters have gone to the conflict [in Syria] and from over 100 countries" while six months prior, the Russian Defense Ministry estimated that there were about "25-30,000 foreign terrorist mercenaries are fighting for ISIL" alone.

The phenomenon causes concerns in the home countries of the foreign fighters. The phenomenon is not new, but the size and widespread origins in this case are.

According to figures collected by the Soufan Group, between 27,000 to 31,000 people including women and children who would not normally engage in conflict have traveled to Syria and Iraq to join the Islamic state and other extremist groups fighting in the region. Reasons that these people join Islamic state or any other extremist group seem to depend on where they come from. Those fighters that come from places like United States or European Union seem to join because they are experiencing some type of identity crisis.This is especially true in regards to first generation and second generation immigrants who join because of the continued marginalization and alienation that they experience from their native peers. Their hope is that joining the Islamic state will give them a sense of purpose and belonging. People who join that are from Islamic countries are likely to join because they want to assist their Muslim brothers that are fighting the Assad regime.

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