The rise of the self-proclaimed “Islamic State” in Iraq and Syria has ushered to the forefront the issue of territories governed by jihadi groups. This article offers an overview of previous and current “jihadi proto-states”, discusses their characteristics and common features, and explores ways of understanding their ultra-aggressive behaviour. Although attempts to form proto-states have been a constant feature of contemporary jihadism over the past 25 years, in the post-2011 Middle East, such attempts have multiplied and succeeded to a greater extent than in the past. These proto-states share at least four distinct characteristics: they are intensely ideological, internationalist, territorially expansive, and irredentist. They also devote significant resources to effective, if harsh, governance. The article argues that forming Islamic emirates and proto-states represents a bid for increased power and influence vis-à-vis rival Islamists. The uncompromising strategy pursued by jihadi proto-states is a result of the intense rivalry with other Islamist rebels as well as the proto-state’s dependence on external (“global jihadi”) constituencies whose allegiance and support can only be maintained by demonstrating a high ideological commitment.