In 1848, the grayling Thymallus aeliani (Valenciennes) was described from Lake Maggiore, Italy, in the north Adriatic basin. Genetic analyses of the mitochondrial control region showed a unique evolutionary history of grayling inhabiting the rivers of northern Adriatic basin, from the upper reaches of the Po River and its left tributaries in the west to the Soča River in the east, which resulted in the designation of this phylogenetic lineage as Adriatic grayling. Consequently, the name T. aeliani was connected to the Adriatic lineage, re-establishing the validity of this taxon. However, the mitochondrial haplotypes belonging to Adriatic grayling were never compared with the type specimens of T. aeliani , as their whereabouts were unknown. In this study, a neotype for T. aeliani was designated using topotypical specimens stored at the Natural History Museum in Vienna. The neotype (NMW 68027:2 labelled as “Lago Maggiore, Bellotti, 1880”) was designated pursuant to the conditions stipulated in Article 75.3 of the International Code of Zoological Nomenclature. Furthermore, the mitochondrial control region of the neotype was compared to haplotypes of the Adriatic lineage and showed high genetic similarity, which therefore connects the species name T. aeliani to the Adriatic grayling. This crucial step in fixing nomenclatural status of this species is very important for its protection and management.