Phoxinus radeki, a new species, is described from the Ergene River (Aegean Sea Basin). It is distinguished from Phoxinus species in Türkiye and the adjacent area by having the scales of the breast, scaled but separated unscaled area anteriorly, short dark rectangular blotches along the lateral line between the lateral line and belly yellowish in both males and females, body depth dorsal fin origin 16–21% SL, caudal peduncle depth 8–10% SL. Additionally, molecular results demonstrated that the new species differed from its closest congeners with a mean genetic distance value of 3.08% (min. 2.82–max. 3.29) and moderately support values in cytochrome b (Cyt b) gene partial sequences (1064 bp.). Further, the species delimitation analysis identified the new species as a single MOTU independent of other Phoxinus species.