Abstract The Gulf of Mexico blue carbon habitats (mangroves, seagrass, and salt marshes) form an important North American blue carbon hot spot. These habitats cover 2,161,446 ha and grow profusely in estuaries that occupy 38,000 km2 to store substantial sedimentary organic carbon of 480.48 Tg C. New investigations around GoM for Mexican mangroves, Louisiana salt marshes and seagrasses motivated our integration of buried organic carbon to elucidate a new estimate of GoM blue carbon stocks. Factors creating this include: large GoM watersheds enriching carbon slowly flowing through shallow estuarine habitats with long residence times; fewer SE Mexican hurricanes allowing enhanced carbon storage; mangrove carbon productivity enhanced by warm southern basin winter temperatures; large Preservation reserves amongst high anthropogenic development. The dominant total GoM mangrove blue carbon stock 196.88 Tg from total mangrove extent 650,482 ha is highlighted from new Mexican data. Mexican mangrove organic carbon stock is 112.74 Tg (1st sediment meter) plus USA 84.14 Tg. Mexican mangroves vary greatly in storage, total carbon depositional depths and in sediment age (to 3500 y). We report Mexican mangrove's conservative storage fraction for the normally-compared top meter, whereas the full storage depth estimates ranging above 366.78 Tg (high productivity in very deep sediment along the central Veracruz/Tabasco coast) are not reflected in our reported estimates. Seagrasses stock of 184.1 Tg C organic is derived from 972,327 ha areal extent (in 1st meter). The Louisiana marshes form the heart of GoM salt marsh carbon storage 99.5 Tg (in 1st meter), followed by lesser stocks in Florida, Texas, finally Mexico derived from salt marsh extent totaling 650,482 ha. Constraints on the partial estuarine fluxes given for this new data are discussed as well as widespread anthropogenic destruction of the GoM blue carbon. A new North American comparison of our GoM blue carbon stocks versus Atlantic coastal blue carbon stock estimates is presented. Graphical abstract Gulf of Mexico blue carbon extent and stock. The amount or sub-regional extent of blue carbon for 6 subregions within the Gulf of Mexico estuaries (and Florida shelf). MN, mangroves; SG, seagrasses; SM, saltmarshes. The extent (hectares), and organic carbon stock (Tg) is listed at each subregion. The underlying blue carbon map used with permission from Chmura and Short (2015) demonstrates the distribution pattern of mangroves (red), saltmarshes (yellow), and seagrasses (navy blue). Unlabelled Image Highlights • Substantial new data requires revision Gulf of Mexico (GoM) blue carbon stock estimate. • Methods: integration new sediment carbon blue carbon results with extent for each estuary. • Mangrove stocks dominate GoM's south half, lessened by anthropogenic impacts. • Saltmarsh carbon stock dominates the Northwestern GoM. • The GoM seagrass sedimentary organic carbon stock is ubiquitous. [ABSTRACT FROM AUTHOR]