Exploration for deep-sea mineral resources began in earnest nearly seventy years ago. For much of that time, experts have claimed that economic viability is about ten years in the future. Today those predictions appear recklessly optimistic, driven by wishful thinking and geopolitical posturing. The expense of mining kilometres below the ocean surface was underplayed, suitable technologies were further off than imagined and falling commodity prices from more accessible sources derailed investment. Early exploration for deep-sea minerals, we have learned, also provided a screen for covert cold war operations, so perhaps public governmental commitment to mining was less strong than it seemed. Today, deep-sea mining has once again clambered up the political agenda. Geopolitics still plays a part in the race to exploit deep-sea minerals, but so too has soaring demand for the metals and rare earth elements that lie on the seabed. Mining corporations have invested heavily, some countries have subsidised experimental operations, and equipment has been designed and manufactured. The International Seabed Authority has licensed multiple claims to explore for minerals and is rushing through guidance on operations. This time, we really do seem on the cusp of a new industry. But in their frenzied efforts to secure a stake in deep-sea wealth, countries have overlooked the need for reflection on the wisdom of mining the ocean floor. Since those minerals first gained world attention, we have learned much about deep-sea life. It is rich, strange, beautiful and diverse. The creatures of the abyss and their habitats are immensely fragile and susceptible to damage and loss. We know enough to foretell that mining will do untold harm to the deep sea and that its impacts will endure for millennia. What we don’t know is how to limit the impacts of mining, or what its unintended consequences might be. There is far more at stake here than national pride or corporate profits. That is why this report calls for deep-sea mining to be paused. The world needs to know far more about deep-sea life and its role in the global environmental processes that keep the planet habitable. We must find this out before the damage is done, not when it is too late.