The thallose liverwort Riccia rhenana is one of three species in the taxonomically challenging “Riccia fluitans” complex that typically occur as floating aquatics. Taxonomic uncertainty has made it difficult to determine the geographical distributions and ecological affinities of these species. A further complication is that these plants are widespread and common in the aquarium trade, raising the possibility of human introductions. Recently we collected R. rhenana from a highly distinctive habitat: a cold, clear, high-flow spring in the Chattahoochee National Forest in northwest Georgia. Subsequent checking of earlier collections revealed that this species appears to be restricted to these unusual habitats within a small area in the northwestern corner of the state and in the vicinity of Pine Mountain in westcentral Georgia. We urge other collectors in the Southeast to seek additional localities for these plants and to reexamine earlier collections with these geographical and ecological correlates in mind.