In contrast to mainstream historiography, secularisation was not a distinct process in nineteenth-century Europe, since the century was a period of religious revival. In the late nineteenth century, in spite of weakening church attendance and rising agnosticism brought on by urbanisation and migration, religion remained attractive for the middle class and social movements related to church membership emerged in politics. In this chapter the diversity of religion in Europe is treated. The author distinguishes between hierarchical and nonhierarchical types of Christian churches, and between four religious regions in Europe. This situation had effects on the relationship between state and religion.