ISIS, or the Islamic State of Iraq and Syria. The Religious extremist terrorist group appeared in the Season Eighteen episode, "Go Fund Yourself". The organization appears again in the Season Nineteen episode, "Naughty Ninjas.
ISIS is a terrorist organization and unrecognized state, known for being militant and religious extremists. They have taken over parts of Iraq and Syria in the Middle East.
The group show support for Eric Cartman's start-up company, the Washington Redskins, much to the unease of Kyle Broflovski. ISIS later withdraws support for the Washington Redskins, after witnessing Dan Snyder (President of the redskins football team) brutalized by the Dallas Cowboys, and boycotts the company.
In "You're Not Yelping", Although the South Park version of the organization isn't seen, real life footage of the group is shown during the Yelper's war on Shi Tpa Town.
In "Naughty Ninjas" They are seen supporting the boys' SoDoSoPa Ninjas, believing they are a part of their religious extremism. The boys in turn believed they were ninjas. Cartman was ecstatic when he learned that ISIS hated Jews, although he still thought they were ninjas.
The members of ISIS appear wearing all black clothes, covering their bodies and faces, as well as military gear. They also all carry black ISIS flags.