Abstract: This article argues that it is not Buddhism, per se, but rather Buddhist extremism, that is responsible for violence against relevant out-groups. Moreover, it suggests that the causes of Buddhist extremism, rather than being determined solely by textual and scriptural justifications for out-group violence, are rooted instead in the intersection between social psychology and theology, rather than organically arising from the latter, per se. This article unpacks this argument by a deeper exploration of Theravada Buddhist extremism in Sri Lanka. It argues that religious extremism, including its Buddhist variant, is best understood as a fundamentalist belief system that justifies structural violence against relevant out-groups. A total of seven of the core characteristics of the religious extremist are identified and employed to better grasp how Buddhist extremism in Sri Lanka manifests itself on the ground. These are: the fixation with maintaining identity supremacy; in-group bias; out-group prejudice; emphasis on preserving in-group purity via avoidance of commingling with the out-group; low integrative complexity expressed in binary thinking; dangerous speech in both soft- and hard-modes; and finally, the quest for political power, by force if needed. Future research could, inter alia, explore how these seven characteristics also adequately describe other types of religious extremism.