This article shows how anti-Catholicism has influenced Danish society and the politics of the Oldenburg Monarchy1 since the Reformation. Scandinavian historians have typically had a materialist approach to history but it is argued that religious convictions played a crucial role. Legislation was dominated by a very explicit anti-Catholicism, also in the written absolutist constitution (Lex Regia, 1665). No persecutions took place and there are several examples of how Catholics were allowed to stay, work and worship, especially in the periphery of the Oldenburg conglomerate state. Absolutism was abolished in 1848-49 but the new constitution still gave a privileged position to the Lutheran state church, which is upheld until today. Although religious tolerance gained ground already in the beginning of the 19th century Lutheranism remained an integral part of Danish national identity.