The Military of the Islamic State is the fighting force of the Islamic State (IS). The total force size at its peak was estimated from tens of thousands to over two hundred thousand. IS's armed forces grew quickly during its territorial expansion in 2014. The IS military, including groups incorporated into it in 2014, openly operates and controls territory in multiple cities in Libya and Nigeria. In October 2016, it conquered the city of Qandala in Puntland, Somalia. It conquered much of eastern Syria and western Iraq in 2014, territory it lost finally only in 2019. It also has had border clashes with and made incursions into Lebanon, Iran, and Jordan. IS-linked groups operate in Algeria, Pakistan, the Philippines, and in West Africa. In January 2015, IS was also confirmed to have a military presence in Afghanistan and in Yemen.

The siege of Kobanî was launched by the Islamic State of Iraq and the Levant on 13 September 2014, in order to capture the Kobanî Canton and its main city of Kobanî in northern Syria, in the de facto autonomous region of Rojava.