A new parasitoid wasp species belonging to the genus Megastylus (Hymenoptera: Ichneumonidae: Orthocentrinae) found in an orchid nursery in The Netherlands is described and illustrated: Megastylus woelkei sp. nov. It was reared from parasitized larvae of fungus gnats (Diptera: Keroplatidae). The biology of this new species and the possibility to use it in biological pest control are briefly discussed.