This dissertation is a study of conflict within the Sunni Jihadi movement (SJM) that attempts to answer the question of why Jihadi groups and individuals engage in internal contestation and infighting when they do. The main empirical focus is the intra-Jihadi conflict, or fitna, that began in 2014 and has continued into the present. This conflict is global in scale and has been dominated by the rivalry between al-Qaida and the Islamic State. The dissertation offers a detailed account of the political and military contestation and conflict between these two groups, which includes within case-studies of how the conflict dynamics affect other Jihadi groups. The research adopts a three-level analytical framework that takes methodological inspiration from social movement studies. It uses this framework to give a comprehensive account of the complex events that have played out on the macro-, meso- and micro-level over the period 2014 – 2019. The empirical materials that provide the basis for the study are, mainly, primary written and audio-visual sources collected through online fieldwork on digital platforms over a seven-year period and interviews with Jihadi ideologues and supporters. The dissertation’s central argument is that intra-Jihadi conflict dynamics are primarily politically driven but religiously informed and articulated. Traditionally, al-Qaida and the Islamic State had differed on smaller religious issues and ideological priorities, yet the major conflict that began in 2014 and evolved over the years can better be explained by certain groups’ hegemonist ambitions. The dissertation stresses that Jihadis are ultimately religio-political actors and illustrates how intra-Jihadi conflict is linked to concrete political contexts and the behaviour of key individuals, who facilitate conflict escalation by producing and disseminating religious justifications for conflict. While internal conflict currently threatens the movement’s internal cohesion, the argument proposed here is that a strong focus on unity nonetheless hinders its implosion.