This dataset is a gathering of historical and contemporaneous records of the medusae stage of Rhizostoma pulmo on its distributional range. The information was compilated to analyze biogeographical patterns and temporal changes of the species population dynamics. This compilation includes data available in websites and peer-review papers. All references are indicated. Data are individualized by month and year from 1810 to 2019, totalizing 7373 records. Longitude and latitude data are reported, as well as the country and the ecoregion (based on Spalding et al. (2007) classification). When the location was detailed (e.g. Bay, Port, Estuary), it is also indicated. The presence/absence category is designated, as well as the abundance or number of individuals reported in the literature. Other extra information (as collector name, sampling method or environmental parameters), when reported, are also provided.

Two different types of data sources were used: scientific literature from peer-review papers and citizen science data. Scientific papers were assembled through an exhaustive search on Google Scholar and Web of Knowledge. The terms used were: ‘Rhizostoma’, ‘Rhizostoma pulmo’, ‘Mediterranean jellyfish’, ‘Mediterranean medusae’, ‘Black Sea jellyfish’, ‘Black Sea medusae’, and the name of each ecoregion followed by ‘jellyfish’, ‘medusae’ or ‘Rhizostoma pulmo’. Only papers where the year of record was indicated were included in this study. The compiled data were qualitative (presence/absence), quantitative (individuals 100m^-3) and semi-quantitative (categories of number of individuals).

A list of the data sources is found in Appendix 1 (Tables S1, S2) of the article Leoni, V.; Bonnet, D.; Ramírez Romero, E.; Molinero, J.C. Biogeography and phenology of the jellyfish Rhizostoma pulmo (Cnidaria: Scyphozoa) in southern European Seas.