'Christian nationalism' refers to the set of ideas in which belief in the development and superiority of one's national group is combined with, or underwritten by, Christian theology and practice. A critique of Christian nationalism is implicit throughout the thought of Soren Kierkegaard, an analysis inseparable from his wider aim of reintroducing Christianity into Christendom. Stephen Backhouse examines the nationalist theologies of Kierkegaard's contemporaries H.L. Martensen and N.F.S. Grundtvig, to show how Kierkegaard's thought developed in response to the writings of these important cultural leaders of the day. Kierkegaard's response formed the backbone of his own philosophical and theological project, namely his attempt to form authentic Christian individuals through the use of 'the moment', 'the leap' and 'contemporaneity'. This study brings Kierkegaard's critique of Christian nationalism into conversation with current political science theories of religious nationalism and reflects on the implications of Kierkegaard's radical approach. While the critique is unsettling to politicians and church leaders alike, nevertheless there is much to commend it to the reality of modern religious and social life. As a theological thinker keenly aware of the unique problems posed by Christendom, Kierkegaard's critique is timely for any Christian culture that is tempted to confuse its faith with patriotism or national affiliation.