As China-United States competition over critical minerals intensifies, interest in deep-sea mining (DSM) in areas beyond national jurisdiction grows rapidly. However, who governs it? This Element offers a pioneering study of the relationship between global and national governance of DSM. Using a constructivist-interpretive approach, it unpacks the international DSM regime established under the UN Convention on the Law of the Sea (UNCLOS), which posits that the deep seabed is the 'common heritage of humankind', and contrasts it with the USA's preference for 'freedom of the high seas'. It explores how the International Seabed Authority (ISA), the USA and China interpret these social constructs' meanings when developing the DSM Mining Code. Although Washington's unilateral action to pursue DSM may speed up the finalisation of the Mining Code, the future of DSM remains uncertain due to mounting concerns about its commercial viability. A moratorium is emerging as the mainstream direction.