I explicate and defend a form of liberal socialist nationalism. It is also a nationalism which is cosmopolitan. Explication and explanation are crucially in order here, for it is not unreasonable to believe that 'cosmopolitan nationalism' and 'liberal socialist nationalism' and even 'liberal nationalism' are oxymoronic. Against that I argue that there is a straightforward understanding of these concepts and their relations to each other that does not have inconsistencies or even paradoxes. Liberal socialism properly understood goes well with cosmopolitanism (both moral and institutional), and there are plausible and attractive forms of both liberalism and socialism that go together. Moreover, the only candidate for a nationalism that would survive careful reflective inquiry is a liberal nationalism: a nationalism which is neither ethnic nor civic. It is widely believed, however, that even a liberal nationalism is incompatible with cosmopolitanism. I contend in a series of arguments that in contexts where nationalism is rightly on the agenda the form that it should take is that of a liberal nationalism, and it is further argued that to be viable, nationalism requires cosmopolitanism.