Introduction The Registry of introduced terrestrial molluscs in Belgium is a species checklist dataset maintained by Thierry Backeljau at the Royal Belgian Institute for Natural Sciences (RBINS). It contains information on all (29) non-native terrestrial molluscs occurring in the wild in Belgium since 1800. The list was originally compiled for EASIN (https://easin.jrc.ec.europa.eu/easin) and is based on a literature survey and information from RBINS. The dataset can be used for researching and managing terrestrial alien molluscs or compiling regional and national registries of alien species. The registry is maintained as a Google Spreadsheet and exported and uploaded here as an Excel file and csv files for each sheet. The dataset is also published for the TrIAS project (Tracking Invasive Alien Species http://trias-project.be, Vanderhoeven et al. 2017) as a standardized Darwin Core Archive, openly available on GBIF (https://doi.org/10.15468/t13kwo). Issues with the dataset can be reported at https://github.com/trias-project/alien-mollusca-checklist Files alien_mollusca_checklist.xlsx: Excel export of the Google Spreadsheet in which the data are maintained. metadata.csv: definitions for the fields in taxa.csv, references.csv, synonyms.csv and vernacular_names.csv, with information about the content, the number of values allowed, the necessity of a controlled vocabulary and whether or not the information is obligatory. taxa.csv: scientific names and higher classification, as well as the species’ presence or absence in Belgium, its first and last observation date, native range, introduction pathway and degree of establishment. references.csv: all references used to compile the dataset. synonyms.csv: synonyms for the scientific names in taxa.csv. vernacular_names.csv: Dutch, French, English and German vernacular names for the scientific names in taxa.csv.