One potential way to geologically sequester captured CO2 emissions is to inject them below the seafloor into marine sedimentary strata where pressures and temperatures would trap the CO2through “self-sealing” gravitational and hydrate-formation mechanisms. Here we map out the worldwide distribution and thicknesses of such self-sealing strata using a comprehensive, global dataset of deep-sea sediment cores in combination with digital grids of ocean floor heat flow, bathymetry, and sediment thickness. Based on our mapping, we estimate that the total bulk sediment volume of self-sealing strata is 63 million cubic kilometers, 0.8–1.4 km3 (or ∼1.3–2.7%) of which are sands with intrinsic permeability suitable for storing CO2. This is enough storage capacity to hold between 1,260–28,500 gigatonnes of CO2, or about 40–1,000 y of total global CO2 emissions. However, the storage capacity is unevenly distributed where it lies within the Exclusive Economic Zones (EEZ) of the world's largest CO2 emitting economies. The United States and India respectively release 16% and 62% of their annual CO2emissions (or 1 Bt/y and 800 Mt/y) within 500 km of self-sealing sands located in their EEZs, while only 6% of the annual emissions from China and the European Union (or 330 Mt/y and 250 Mt/y, respectively) occur within this distance.