The brown marmorated stink bug, Halyomorpha halys (Stål, 1855) (Hemiptera: Pentatomidae), is native to East Asia and was first detected in Europe in 2004 in Switzerland. In Hungary, it was first recorded in the capital, Budapest, in 2013. Halyomorpha halys is an invasive polyphagous species, which is able to cause severe damage to a wide range of crops, and it is also considered an urban pest in America and Europe. By 2018, the status of H. halys as an agricultural pest causing major damage to cultivated plants in Hungary has been confirmed only by a single study carried out in 2016 at a farm located in Budapest. In the past few years, the pest has received significant media coverage in Hungary due to the increasing nuisance problems. However, detailed and reliable information on its spread were still missing. Therefore, in 2016, an extensive survey was initiated to obtain data on the distribution of H. halys in the country. This study was primarily based on the use of citizen science, which was completed with information requests from the members of professional organizations as well as active data collection by the authors. The results of this first extensive survey revealed the wide distribution of H. halys in Hungary, with mass occurrence of the species at several locations throughout the country, especially in the region of Budapest. These data highlight the rapid dispersal of H. halys and call for attention to the threat the pest poses to Hungarian plant production. © 2018 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany.