Hemidiaptomus (Gigantodiaptomus) superbus (Schmeil, 1895) was found in a temporary pool in the Pineta di Classe coastal pine-wood (Ravenna, northern Italy). This is the first official record of a species belonging to the subgenus Gigantodiaptomus of Italian fauna, and it widens the known distribution of this rare diaptomid to the Mediterranean basin. In order to supply data on this rare and poorly known species, original drawings for the Italian population have been provided, and some overlooked morphological features have been highlighted. In light of the growing evidence of the existence of a number of cryptic species in the Diaptomidae family, and considering the variability observed in the ornamentation of the fifth pair of female legs, the ribosomal DNA marker 16S was used to compare the specimens collected in Italy with those from the terra typica of the species. Molecular data confirmed the strict conspecificity of the two populations being studied. The environmental parameters relating to the new Italian site are described and compared with the few data currently available in the literature. A careful review of all the published data dealing with H. (G.) superbus has been performed, and the paucity of recent records is stressed, together with the opportunity to support dedicated conservation measures for the protection of this species.