The European Marine Observation and Data Network (EMODnet) is a web portal that brings together marine data, data products and metadata from diverse sources within Europe in a uniform way. It was initiated by the European Commission in response to the EU Green Paper on Future Maritime Policy, launched in June 2006. The main purpose of EMODnet is to unlock fragmented and hidden marine data resources and to make these available to individuals and organisations without restriction, except in special cases. The primary motivation for EMODnet is to stimulate investment in sustainable coastal and offshore activities through improved access to quality-assured, standardised and harmonised marine data.

Once fully operational, the EMODnet web portal will provide access to various sub-portals, each of which pertains to a specific thematic group, with some overlap. The thematic groups allow the appropriate experts to define a common structure for the data within each theme, thus ensuring interoperability. Presently, there are seven sub-portals under construction: the Hydrography Portal, the Geology Portal, the Physical Parameters Portal, the Chemical Portal, the Biological Data Portal, the Physical Habitats Portal, and the Human Activities Portal. The result will be a portfolio of seamless data layers across European and adjacent sea basins. Individuals and organisations are encouraged to contribute data on a voluntary basis to ensure that the system remains current.