Since the mid-twentieth century, religion in Europe has faced three inter-related trends: the waning of Christianity, increasing secularization, and rising levels of diversity stemming from growing globalization and changing migration patterns. As a result, all European states confront the same broad question: how to adapt existing church–state relations and norms of secularism to an extra-Christian religious diversity that the continent has not known before. At the same time, Europe features a ‘bewildering variety’ of political and institutional connections when it comes to the governance of religious diversity, reflecting different historical inheritances. To make sense of this, this chapter discusses these dynamics in relation to three processes: the politicization, institutionalization, and securitization of religion and divides its discussion into three confessional regions—a majority Protestant North-West, a majority Catholic South, and a majority Orthodox East—in order to analyse how, from their many different starting points, European states are addressing contemporary religious diversity.