This chapter examines the complex relationship between religious fundamentalism and violent extremism, focusing on the socio-cognitive processes involved in radicalization. In the central part of our analysis, we explore how religious fundamentalism may contribute to violent extremism. Our investigation reveals that the relationship between these two variables is mediated by some group-related factors and ideologies (e.g., out-group hostility, perceived superiority, collective narcissism, ideological extremism, and extremist networks). Importantly, religious fundamentalism does not always lead to violent extremism; it is moderated by some situational and contextual factors (e.g., perceived injustice, perception of threat, and group tightness). We then discuss the implications of these findings for counter-violent extremism programs. We argue for a comprehensive approach, advocating for integrated interventions that combine ideological, psychological, and economic strategies. This assertion stems from the recognition that the drivers of violent extremism extend beyond religious narratives to include psychological factors and subjective and economic deprivation. As such, we caution against an approach that disregard nonideological aspects, as it may weaken the effectiveness of interventions. © Cambridge University Press & Assessment 2025.