From a legal point of view, the issue of defining terrorism is particularly controversial and, to date, no generally accepted definition exists. For example, many legal documents normally define terrorist acts in a quasi-pleonastic way, saying that they are committed with a specific terrorist aim. This is even more evident in relation to the religion-inspired terrorism, which underlines the fact that we barely know the real-concrete relationship between the existing forms of terrorism and religion, namely Islam. The same can be said about the notion of religion-inspired radicalization, which the European institutions and the Member States unsuccessfully attempt to define. The article tries to address this issue, focusing the attention on the Italian case, also taking into account the Country’s experience in combatting domestic terrorism and organized crimes. That is the reason why Italy’s experience represents one of the most interesting cases in Europe and in the West.