Seabed substrate maps of the European marine areas including (e.g. the Baltic Sea, the Greater North Sea, the Celtic Sea, the Iberian Coast, and the Mediterranean Sea within EU waters). The maps are collated and harmonized from seabed substrate information within the EMODnet-Geology III project. Where necessary, the existing seabed substrate classifications (of individual maps) have been translated to a scheme that is supported by EUNIS. This EMODnet reclassification scheme includes at least five seabed substrate classes. Four substrate classes are defined on the basis of the modified Folk triangle (mud to sandy mud; sand; coarse sediment; and mixed sediment) and one additional substrate class (rock and boulders) was included by the project team. If the original seabed substrate dataset has enabled more detailed substrate classification, classifications with 7 and 16 substrate classes might be available. The EMODnet-Geology III project started in 2017 with 39 marine departments of the geological surveys of Europe (from 30 countries), with an objective to assemble marine geological information from all European sea areas.