The Hellenic Centre for Marine Research (HCMR) is a governmental research organisation operating under the supervision of the General Secretariat for Research and Innovation (GSRI) of the Ministry of Development and Investments. The HCMR comprises three Research Institutes: The Institute of Marine Biology, Biotechnology and Aquaculture (IMBBC), the Institute of Marine Biological Resources and Inland Waters (IMBRIW) and the Institute of Oceanography (IO). The Hellenic Centre for Marine Research is the Greek national agency in charge of the study and the monitoring of the marine and freshwaters (physical oceanography and marine biology). Since its inception, a team was created in Crete to monitor marine biodiversity, and to develop databases for marine biodiversity. HCMR became the Regional OBIS Node for the Mediterranean and the Black Sea in 2006, providing about 140 datasets and 34017 occurrence records. Later, the datasets from the Black Sea were removed and managed by a dedicated Regional OBIS Node. In 2013, supported by the Ministry of Research, HCMR joined the European LifeWatch network that aims at developing a distributed research e-infrastructure for biodiversity data and data observatories under the ESFRI programme. LifeWatchGreece has constituted a large network of almost all institutions in Greece working on biodiversity including terrestrial ecosystems. Among other tasks, it has in charge to continue to maintain and develop the MedOBIS node, and also to establish the National GBIF node (in progress). MedOBIS provides access to data from a wide range of sources and time periods, including new and historical data sets. It actively contributes to global scientific effort for FAIR and OPEN data. When consulting and using information and data from MedOBIS, the general citation is as follows: MedOBIS data. Mediterranean node of the Ocean Biodiversity Information System (EurOBIS). Available online at ipt.medobis.eu . When using data from MedOBIS in reports, posters, publications etc., please cite the relevant data sources. A suggested citation for each dataset is included in the metadata.