The Registry of non-native species in the Two Seas region countries is a species checklist dataset published by the Research Institute of Nature and Forest (INBO). It contains information on 6.643 taxa occurring in the Two Seas region countries (Great Britain, France, Belgium and the Netherlands). This dataset represents a registry of species that are not native, but recorded to live in the wild in at least one of the four countries and is the result of the screening of 55 national and international print and online sources. The checklist has been published as a data paper by Zieritz et al. (2014, https://doi.org/10.3897/neobiota.23.5665), where it can be downloaded as supplementary material. Here it is published as a standardized Darwin Core Archive and includes for each taxon: the scientific name, higher classification and stable taxon identifier (in the taxon core), the (confidence regarding the) presence of the species in each of the four countries, whether the species is native or introduced (establishment) (in the distribution extension) and coarse habitat information (in the species profile extension). Issues with the dataset can be reported at: https://github.com/trias-project/rinse-registry-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 https://twitter.com/LifeWatchINBO. 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.