Complete report of the genetic analyses performed in a study investigating the genetic diversity of the Brown Marmorated Stink Bug Halyomorpha halys in Belgium. This study was submitted to NeoBiota with the following title: Distribution and genetic diversity of the invasive pest Halyomorpha halys (Hemiptera: Pentatomidae) in Belgium. Abstract: The brown marmorated stink bug, Halyomorpha halys, native to East Asia, is an invasive pest of economic importance. It has mainly invaded North America and many European countries and is further expanding its range in Europe. In Belgium, it was first observed in 2011. Halyomorpha halys is known to cause severe damage in vegetable crops and in commercial fruit orchards. Therefore, a dramatic and unmitigated expansion of H. halys in Belgium could lead to significant economic implications for fruit production. In this study, occurrence data of H. halys since its first observation in Belgium was analysed together with molecular information to map the populations and evaluate the genetic diversity of this pest. The genetic diversity of H. halys in Belgium was compared to data from other invaded and native countries reported in previous studies to identify possible invasion routes. The analysis of 1176 bp of mitochondrial DNA cytochrome c oxidase I and II genes (COI and COII) led to the discovery of two novel COI-COII haplotype combinations currently unique to Belgium. The invasion of H. halys in Belgium is likely the result of multiple and ongoing introductions from its native region and from already invaded countries in Europe, in particular Italy. The expansion of the brown marmorated stink bug populations in Belgium is recent and ongoing. The brown marmorated stink bug appears to thrive most in northern Belgium.