Potamon fluviatile and covers parts of many countries with a Mediterranean coastline. It is found in mainland Italy and on the Balkan Peninsula from Dalmatia to the Axios River in Greece. It is also found on a number of islands, including Sicily, Malta and Gozo, the Ionian Islands, Aegean Islands, Sporades and Andros in the Cyclades. Although the species as a whole is widespread, it is declining in numbers, and these insular populations are particularly vulnerable. "Potamon fluviatile" is widely distributed in much of mainland Italy, especially in the provinces of Trento, Lombardy, Veneto, Liguria, Tuscany, Umbria, Lazio, Campania, Apulia, and Calabria,
Potamon fluviatile and across Central Asia as far east as northwestern India. The populations of "P. fluviatile" on the Peloponnese, Kefalonia, and Zakynthos may represent a separate, cryptic species, and the population from the Peloponnese was described in 2010 as "P. pelops". "P. fluviatile" was formerly divided into three subspecies: "P. f. algeriense", "P. f. berghetripsorum" and "P. f. fluviatile". The first two of these live in North Africa, and were later combined and separated from "P. fluviatile" as the species "Potamon algeriense". By 1983, the nominate subspecies (equivalent to the current circumscription of the species "P. fluviatile") had been divided into