The spring-snail genus Bythinella is a diverse group of minute operculate gastropods, usually restricted to springs and widely distributed in Europe. Species are primarily delineated based on shell characters such as size or overall shape. Nevertheless, studies based on molecular and morphological approaches show that these characters can be highly variable and do not necessarily have taxonomic significance. In this paper we formally describe and name, according to the requirements of the International Code of Zoological Nomenclature, a species identified by previously published phylogenetic analyses and by a barcoding gap approach based on the mitochondrial COI gene. The molecular results suggest this species is a micro-endemic species currently recognized only from south-western France at its type locality. We also highlight that the barcode approach considerably reduces the number of valid species in this region, and that a strictly shell-based taxonomy probably overestimates the species richness of the genus Bythinella.