ISIS has proven its terrorist ideology on the ground in Iraq, Syria, and other parts of the world at least during the period (2014-2017) through its effective control of various territories, and the declaration of its entity, "caliphate" in 2014. It also presented itself as a new generation of "terrorists," in a terrorist structure more developed than the well-known terrorist organizations. Despite its ideology, modeling, "geographical and media" intimidation, recruitment, and cross-border threats with high levels of opportunism and barbarism, ISIS is a terrorist phenomenon with a new template that combines ideology and spatial and temporal control on the ground. It added a new dimension to worldwide terrorist activity despite international efforts to combat terrorism. This paper examines the intellectual references and literature that crystallized the organization's ideology and made it controversial for its bloodiness and barbarity. The descriptive analytical approach of contemporary intellectual texts and literature is used to identify the most prominent writers and intellectuals who helped build ISIS's terrorist ideology, either through media or the terrorist organization's acts on the ground. The study found that ISIS' intellectual entity predated its appearance in Iraq in 2003. Taking advantage of opportunism to boldly frame and strengthen ideology and ideas is the difference. Understanding the organization's terrorist ideology, intellectual foundations, and religious motives helps us counter their control, mobilization, and recruitment and develop a medium- and long-term strategy.