This book postulates that the rise of right-wing populism in the West and its references to religion are less driven by a resurgence of religious fervour, than by the emergence of a new secular identity politics. Based on exclusive interviews with 116 populist leaders, key policy makers and faith leaders in the USA, Germany, and France, it shows how right-wing populists use Christianity as a cultural identity marker of the 'pure people' against external 'others' while often remaining disconnected from Christian values, beliefs, and institutions. However, right-wing populists' willingness and ability to employ religion in this way critically depends on the actions of mainstream party politicians and faith leaders. They can either legitimise right-wing populists' identitarian use of religion or challenge it, thereby cultivating 'religious immunity' against populist appeals. As the populist wave breaks across the West, a new debate about the role of religion in society has begun.