This paper reflects on the enduring relevance of religion and nationalism in the survival of modern nation-states. I develop a framework that puts these nonrational, nonmaterial cultural sources at the center of the analysis to explain why and how they are relevant to the continued persistence of modern nation-states. The three-track framework introduced here generates conceptual apparatuses that help us understand the processes and dynamics involved, namely: ethnoreligious nationalism, securitized minorities, and sacralized security superstructures. Applying the framework to Southeast Asia, I demonstrate why ethnicized religion and nationalism remain vital to the imagination of contemporary nation-states; and how they are crucial to the construction of structural institutions designed to preserve the conceptual cohesion and material integrity of these units. I conclude that the continuity of modern nation-states has been underwritten by the cultivation of ethnoreligious nationalism, securitization of the ‘threat’ of othered minorities, and sacralization of security superstructures.