This dissertation argues that the waters of the English Channel and North Sea constituted a coherent region of political, geographical, and human life in the late sixteenth and early seventeenth centuries. It examines a large corpus of manuscript and printed maps, sea-charts, portolan charts, navigation manuals, and other works of geography to determine what the Channel was named, when, and by whom, demonstrating how nomenclature and systems of toponyms were wielded as political tools by nationalist cartographers. It traces changes in how the region was known and represented over two centuries, and how cartographic practices and sailing technology shifted along with those changes, to the benefit of domestic and overseas trade and nascent empire-building for England, France, and the Netherlands. It posits the existence of at least two ‘maritime states’ on and next to Channel waters, as the Dutch Sea Beggars and the Brittany port town of Saint-Malo sought to carve out nationhood for themselves based almost solely on the deployment of marine power. Finally, it considers how events and experiences in the Channel can inform and support current developments in the field of the ‘blue humanities.’ Many aspects of the work seek to complicate, and in some places to undermine, the common truism that ‘knowledge is power,’ asking what representations of knowledge might have produced what sort(s) of power on early modern European maps.