The term, ‘fundamentalism’, today names a broad religio-political perspective found in most, if not all, major religions. Most disturbingly, it is associated with variant forms of religious extremism and thus religiously-oriented terrorism. And it is Islamic modalities of terrorism that, rightly or wrongly, have come to take centre-stage in current world affairs. Arguably, however, the religious fundamentalism with which Islamist extremism is associated follows an identifiable paradigm that has wider applicability. It denotes, among other things, a paradigm that paves the way from the relative harmlessness of an idiosyncratic and dogmatic belief system, to the harmful reality of religiously driven and fanatically followed pathways to terrorist activity. This paper will discuss the phenomenon of fundamentalism and attempt to describe and analyse the paradigm of religious fundamentalism. It is the cumulative dynamic of fundamentalism which informs the emergence of religious extremism and terrorism.