Separation of church and state is one of the key concepts in contemporary debates in increasingly secular democracies like the Netherlands. It is not only used to describe the legal and political arrangements between the state and religious organizations, but is also part of a larger discursive struggle over national identity and the meaning of citizenship. This article traces the history of the concept of separation of church and state in the Netherlands since the eighteenth century. First, it shows how the concept has always been a contested one. Second, it argues that the current framing of separation of church and state as a fundamental value of Dutch society is relatively recent and is connected to growing secularism and the position of Islam in Dutch society.