Limiting future temperature increases and associated climate change requires immediate action to prevent additional carbon dioxide being released into the atmosphere and to lower the existing atmospheric carbon dioxide load. This could be advanced through carbon capture and storage (CCS), which involves collecting carbon dioxide that would otherwise be released by power plants or similar facilities and injecting it into underground geologic formations, where it will remain permanently sequestered. The techniques developed for CCS can also be used to sequester carbon dioxide that has been removed from the atmosphere using direct air capture or other negative emission technologies. Past CCS research has primarily focused on sequestering carbon dioxide onshore, for example, in depleted oil and gas reservoirs or deep saline aquifers. This Article explores the legal framework governing sub-seabed carbon dioxide injection (offshore CCS) in U.S. and Canadian waters, particularly the Cascadia Basin, where there is a large sub-seabed basalt rock formation with significant storage potential.