ABSTRACT. – Over the last few decades, reports of the freshwater jellyfish Craspedacusta sowerbii have increased worldwide. This invasive alien species, native to China, has invaded France’s freshwater systems. The present article reports the following information regarding this jellyfish: (i) distribution across the French metropolitan territory, (ii) life cycle, physiology and reproductive mode, and (iii) ecology and impact. The main aim of this article is to establish an updated inventory of invaded areas in order to better understand how and why its occurrence is reported with increasing frequency in France. In the 1970s, only 36 sites for Craspedacusta sowerbii were identified. In our study, we observed a widespread distribution of these freshwater jellyfishes in France: 123 sites. Craspedacusta sowerbii was mainly observed in closed ecosystems (ponds – temporary or permanent; basins): 38 ponds, 35 lakes, 14 water-filled quarries and 7 basins and a few in rivers and canals (29 stations).