The relationship between religion and national identity is a contested topic in public debates about cultural diversity and immigration. In sample surveys only a minority the British population identify themselves as belonging to a Christian religion, and far fewer practise their faith. Nevertheless, nearly a quarter of the population think it is important to be Christian to be truly British. This study explores the complex relationships between religious and national identities in Britain, using data from the 2008 British Social Attitudes Survey. Three different forms of national identity were identified through factor analysis: civic-symbolic, cultural-aesthetic and ethnic national identity. Ethnic national identity is the only dimension of national identity that is positively associated with thinking it is important to be Christian to be British. While churchgoing Christians are more likely to feel national in response to secular cultural symbols, they are less likely to associate religion with nationality than those with a nominal Christian affiliation. The results indicate that Christianity has cultural significance for national identity primarily as a proxy for ethnic identity.