Description, figures and metric data on the main diagnostic criteria are given for Dactylogyrus ostraviensis n. sp., an organism parasitizing the gills of Barbus conchonius in aquarium conditions. The shape of the hard parts of the haptor, particularly the ventral bar and the main part of the inner roots of the anchors and also the copulatory organ, differ from those in previously described species parasitizing freshwater fishes of the Old World.