The article deals with the principal peculiar differences between Islam as a religious system versus Islamism as a political ideology. Despite of some religious roots connecting Islamism with the theological system of Islam at the early stage each subsequent step of Islamist progress was in its way to the political transformation as an ideology but not a religious phenomenon. So it means the differentiation of Islam as a religious idea and Islamism as a political concept. This work analyses the origins and transformations of Islamism in its different types including the Sunni and Shi’i branches. The links between Islamism and Salafiya are revealed. The Muslim Brotherhood is presented as an example of a modern transnational Sunni Islamist organization. The article reveals some social reasons and basement of Islamist radicalization which intensified political character of this movement. The main contradiction between Islamist movement and state is focused on the religious sense of the society contra secular character of the State. As a result a lot of Islamist groups legalize violence against their state authoriСодержание номераties and leaders in Jihadism form. The article describes some historical samples and ideological theses used by Islamists. As a result the Islamist terrorism is classified as an extreme antihuman political form of Islamism that is ultimately far from the Religion.