This paper reconciles a substantial gap in legal scholarship: the Islamic State's (ISIS's) unrecognized genocide against Shia Muslims. Unlike ISIS's crimes against Yazidis, no substantial legal analysis on ISIS's Shia victims has been published. And while there are popular initiatives demanding ISIS's violence against Christians be recognized as genocide, there are no parallel movements on behalf of ISIS's Shia victims, despite a much stronger legal claim. As this paper expands, ISIS's genocide against Shias is unambiguous; Shia Muslims plainly comprise a protected religious group, ISIS has been transparent in terms of its genocidal intent, and ISIS's systematic killing of Shias clearly constitutes genocidal conduct under the Genocide Convention. Over the course of this paper, I advance this thesis, demarking clear parallels with ISIS's well-established genocide against Iraq's Yazidis. I also explain the significance of the legal community's neglect of ISIS's Shia victims.