This essay deals with religious fundamentalist movements engaged in democratic politics: a phenomenon still not thoroughly analyzed by comparative political science. First of all, it proposes a definition of religious fundamentalism which can be suitable for political science research (connecting the existing theories about fundamentalism to the literature about collective identities and social movements: particularly the political opportunity structure and resource mobilization models). Later, it takes into account four cases of religious fundamentalist movements in democratic regimes: the Christian right in the USA, the sangh parivar in India, the Jewish religious nationalist movement in Israel, and the Islamist movement in Turkey. In this section, the main features of the movements’ mobilization and their political strategies are singled out. The work eventually tries to find out common patterns by comparing the different movements, their relationship with politics, and their impact on public policies. Particularly, it proposes a typology of fundamentalist movements in democracy, according to their political strategies and the ideological orientation of their issues.