Polymetallic nodules are naturally occurring, rock-like formations on the deep ocean floor that contain high concentrations of critical clean-energy metals like cobalt, nickel, copper, and manganese. As demand surges for EV batteries, renewable infrastructure, and grid-scale storage, these nodules represent a promising way to diversify supply beyond increasingly constrained land-based sources—potentially with less land disturbance and lower overall carbon intensity when developed responsibly.