We report the first records to Denmark of the hoverfly Cheilosia fasciata Schiner & Egger, 1853. The larvae live as leaf miners on Allium ursinum L. (ramsons). The mines are conspicuous and easily recorded. We first found larvae and mines in a forest on the island of Falster in south-eastern Denmark in 2014. Search for larvae and adults during the 2015 season across Denmark – assisted by numerous volunteers – resulted in a total of four inhabited forest sites, all on Falster and within a distance of 10 km. Thus, the species is most likely a recent immigrant from northern Germany. It will probably continue to spread in the years to come.