This book begins with an ending: the historical moment in the eighteenth century when Britain succeeded in cleansing the Atlantic of its pirates. The argument that follows concerns a movement that, on the contrary, refused to end. It documents the pirate's persistence as a cultural memory of resistance to social, political, and economic oppression, and finds him to be just one instance of a revolutionary spirit that emerges in some surprising places during the Romantic period: in prophetic pamphlets, in travel narratives about Jerusalem and Africa, in William Blake's visionary poetry, and in Lord Byron's Eastern romances. The radicalism of these texts consists in their imagination of space beyond the terms of nationalism and territory; their power is that they force us to recognise the incongruence between mapped and lived space. I therefore move away from an account of radicalism that takes the nation as its primary point of contention and focus instead on figures who fall outside of the terms that nationalism imposes. Prophets and pirates are apt figures because they operate outside of the literal or figurative boundaries of the nation: prophets live in the nation of God, and pirates live in motion. Their particular and pervasive radicalisms are enabled by their status as outsiders to the nation; their practices of settling land and claiming ships in defiance of national authority become material interferences in a system of nationalised space. I trace these varied forms of geographical radicalism as well as the systems in which they are inscribed, thereby revealing the contours and limits of territorial sovereignty. And so, while varying in topic and form, my assembled texts share something crucial: their documentation of a radicalism that is mobile, informed by a conception of space as movement rather than containment, inscribed in an increasingly visible Atlantic network.