This is an open access title. It is available to read and download as a free PDF version on Oxford Academic and is made available under a Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International licence. Eighty years after the first nuclear weapons were exploded over the Japanese cities of Hiroshima and Nagasaki, the world has moved into a new, more dangerous, contested, and complex era. We can think of this as a Third Nuclear Age^—^fundamentally different from the Cold War and post-Cold War worlds that preceded it. A combination of rapid technological change in weapons systems and the nuclear information space that will impact deterrence, escalation, and proliferation; a move towards a more fragmented, multipolar world, and perhaps the end of the liberal international order; a breakdown in arms control and the sense of shared nuclear responsibility and restraint; and increased appetite for nuclear technologies to meet climate, developmental, and scientific demands, as well as clashing visions about the shape and prospects for our nuclear world across all levels of society, all point to a future in which nuclear politics return as a defining feature of the Anthropocene and perhaps everyday life. After what seems like a period of relative peace and stability, nuclear weapons are back at the heart of global politics and remain the only way that humans can destroy modern civilization in a matter of hours. The question is whether we as a species are prepared to meet the challenges of this new era.