This article explores the international political thought of one of the most prominent late Victorian public intellectuals, John Robert Seeley (1834–95), the Regius Professor of Modern History at Cambridge, and author of the best-selling The Expansion of England (1883). Challenging conventional readings of Seeley, I argue that his vision of global politics must be located within the wider frame of his views on the sacred, and that he is seen best as articulating an intriguing political theology of international relations. In particular, I argue that instead of interpreting him as a realist, as has traditionally been the case, his position is classified most accurately as ‘cosmopolitan nationalism’. Only by situating him in the intellectual context(s) of his time is it possible to provide an adequate account of the identity of his political thought.