The Ellenic Network on Aquatic Invasive Species (ELNAIS) was established in 2007 by the Hellenic Centre for Marine Research (HCMR), recognizing the need for national and international cooperation in research, scientific information exchanges and management of aquatic (marine and freshwater) NIS in Greece. It was further developed, updated and translated in Greek under the project 4ALIEN in 2022. According to the latest ELNAIS census, a total of 242 marine NIS had been recorded in Hellenic waters by Septemeber 2020 (Zenetos et al. 2020). Detailed distributional data of marine NIS in Greece are stored in the ELNAIS database which is continuously updated with new data from published and grey literature and new observations by a network of more than 80 contributing experts (see experts details) from several disciplines (e.g. research/academic institutes, non-governmental organizations) and well as citizen science data.