How France integrated the seafloor into its national territory through an interplay of science, technology, and geopolitical ambition during the Cold War.   Beneath the surface of the seas and oceans lies a territory as important for human societies as the exposed land and the airspace above them: the seafloor. Our daily life is inextricably linked to the seafloor and its resources, from global telecommunications infrastructure to offshore oil and gas extraction to strategic mineral mining.   By focusing on France, a country with an underwater territory seventeen times larger than its emerged lands, New Deep Territories explains how the seafloor emerged as a territory during the second half of the twentieth century. Beatriz Martinez-Rius traces the evolution of the country’s seafloor exploration and the motivations that fueled it from the aftermath of World War I to the late 1970s. In the early 1960s, the seafloor, instead of colonial territories, came to be seen as a source of natural resources. The French government, corporations such as oil companies, and scientists all imagined future uses of the seafloor, and these ever-evolving aspirations drove the development of technologies, techniques, and scientific fields that built up the submerged territory. Government officers and industrial stakeholders massively invested in technoscientific development to prepare for a future reliant on seafloor resources, including oil, gas, and minerals, well before it was technologically possible, economically feasible, and legally acceptable to extract them. The future they envisioned did not arrive, but their investment resulted in an unprecedented understanding of the ocean’s crust. Today, once again, national governments, international organizations, and private stakeholders are turning their attention to the seafloor.