The trematode fauna of Potamopyrgus antipodarum, an introduced and invasive gastropod mollusc species native to New Zealand, was studied in Mont Saint Michel Bay (France). The study revealed, for the first time in Europe, the occurrence of larval digenean species, Sanguinicola sp., a blood fluke of fish never previously recorded in this prosobranch. Phase contrast and scanning electron microscopy was used to investigate the morphology of the parasite. Hypotheses on the origin of the P. antipodarum–Sanguinicola sp. association are discussed in relation to the history of invasion of the gastropod into brackish and fresh waters and the structure of local gastropod communities.