Observations.be - Non-native species occurrences in Wallonia, Belgium is a species occurrence dataset published by Natagora. The dataset contains over 190,000 occurrences of animal, plant and fungal non-native species, recorded by volunteers (citizen scientists), mainly since 2008. The occurrences are derived from the database http://www.observations.be, an initiative from the nature conservation NGO Natagora (https://www.natagora.be) in collaboration with Stichting Natuurinformatie and Natuurpunt. Standardized information regarding the occurrence's sex, reproductiveCondition, behavior, occurrenceRemarks, and samplingProtocol is included as well. Issues with the dataset can be reported at https://github.com/trias-project/natagora-alien-occurrences Generalized and/or withheld information: for some occurrences, location information is generalized to grid cells, as requested by the observer (usually to avoid disturbance or collecting). Observer name, toponyms, and photographs are not included in the published dataset, but are known in the source database. We have released this dataset to the public domain under a Creative Commons Zero waiver. We would appreciate however, if you read and follow these norms for data use (https://www.natagora.be/donnees_naturalistes_usage) and provide a link to the original data set whenever possible. If you use these data for a scientific paper, please cite the dataset following the applicable citation norms and/or consider us for co-authorship. We are always interested to provide more information or know how you have used the data, so please contact us via the contact information provided in the metadata or via biodata@natagora.be.