This thesis investigates the relationship between religion and right-wing populism in Western Europe and North America, with a specific focus on Germany, France and the United States. From the carrying of crosses at rallies to a new rhetoric centred on the defence of “the Judeo-Christian West”, right-wing populist movements on both sides of the Atlantic have made increasing use of Christian symbols and language. This thesis seeks to comprehend this dynamic by exploring the following research questions: What are the social and demographic roots behind the rise of right-wing populist politics in Western democracies? How and why does religion feature in right-wing populist rhetoric and strategies? How do Christian communities react to right-wing populists’ religious-laden rhetoric and what is the role of mainstream parties and religious leaders in shaping these responses? Finally, what do these trends mean for the role of faith and religious institutions in Western democracies going forward? Drawing on new survey data, party manifestos and 115 in-depth elite interviews with right- wing populist leaders, mainstream party politicians and senior religious officials in Germany, France and the United States, this research deploys a demand- and supply-side framework to address these questions. On the one hand, it revisits social cleavage and secularisation theory to investigate how new socio-cultural, economic and religious developments in the electorate of the three case studies (demand-side factors) have created demand for right-wing populist politics and their religious references. On the other hand, it relies on new empirical evidence from speeches, manifestos and elite interviews to examine how on the supply-side, right-wing populist leaders seek to harness this demand and how their ability to do so is determined by the actions of other political and religious supply-side actors such as mainstream parties and religious leaders. This thesis contributes to existing theoretical debates surrounding the rise of right-wing populism and the shifting role of religion in Western politics by showing that in Germany, France and the United States right-wing populists often employ Christianity as a cultural identity marker in order to mobilise voters around a new social cleavage centred around the question of identity. However, in doing so they frequently remain distanced from Christian doctrine and institutions, and instead seek to combine cultural references to Christianity with secular policy stances, suggesting a secularisation of Christian symbols rather than a resurgence of religion. The findings of this thesis also suggest that the reactions of mainstream political parties and churches can have a significant impact on right-wing populists’ ability to effectively harness religion for political gain. In particular, religious leaders appear able to either legitimise right-wing populist appeals to religion, or to erect powerful social taboos against these movements and their references to religion among Christian voters, thus creating in some cases a “vaccination effect” of religion against voting for right-wing populist candidates. All this suggests that as the populist wave breaks across the West, a new debate about the future role of religion in Western societies has just begun.