Invasive species - Ruddy duck (Oxyura jamaicensis) in Flanders, Belgium is a sampling event dataset published by the Research Institute of Nature and Forest (INBO). It contains information on 107 sampling events with 88 validated occurrences of invasive ruddy duck (with 2 extra occurrences reporting on white-headed duck) starting from 2009. These occurrences mainly originate from observations or cullings (through shooting or trapping) of individuals associated with official control actions in Flanders, North Belgium in response to the Bern Convention Action Plan on ruddy duck eradication (Robertson et al. 2015; Bern Convention 2016; Hall 2016). The data are used for feeding the Flemish biodiversity indicator on the progress of ruddy duck eradication. Also, they are used for official reporting to the Bern Convention Action Plan on the eradication of ruddy duck from the Western Palearctic (Bern Convention 2016; Hall 2016) and, as the species is included in the list of invasive species of Union Concern since 2016, for reporting to the EU IAS Regulation (1143/2014) (European Union 2014). The data are also used for research purposes. Here the dataset is published as a standardized Darwin Core Archive and includes for each event: a stable eventID, date and location of observation, and a short description of the sampling protocol (in the event core), supplemented with specific information for each occurrence: a stable occurrenceID, the scientific name and higher classification of the observed species, the number of recorded individuals, sex, life stage, and a reference to the observer and identifier of the record (in the occurrence extension). Issues with the dataset can be reported at https://github.com/inbo/data-publication/issues 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).