The Checklist of alien species in the Scheldt estuary in Flanders, Belgium is a species checklist dataset published by the Research Institute for Nature and Forest (INBO). It contains information on 61 invertebrate alien species occurring in the Belgian Scheldt estuary, detected between 1835 and now. Here it is published as a standardized Darwin Core Archive and includes for each species: the scientific name, higher taxonomy, stable taxon ID (in the taxon core), the year of first introduction and/or last assessment in Flanders (given as a year or year range in the event date in the distribution extension), coarse habitat information (in the species profile extension) and the native range(s), pathway(s) of introduction and degree of establishment in Flanders (in the description extension). Issues with the dataset can be reported at https://github.com/trias-project/alien-scheldt-checklist We have released this dataset to the public domain under a Creative Commons Zero waiver. We would appreciate it if you follow the INBO norms for data use (https://www.inbo.be/en/norms-data-use) when using the data. If you have any questions regarding this dataset, don't hesitate to contact us via the contact information provided in the metadata or via opendata@inbo.be. This dataset was published as open data for the TrIAS project (Tracking Invasive Alien Species http://trias-project.be, Vanderhoeven et al. 2017), with technical support provided by the Research Institute for Nature and Forest (INBO). It is selected as one of the authoritative sources for the compilation of a unified and reproducible checklist of alien species in Belgium.