Five species of the Oulema melanopus group are recognized in the western Palaearctic Region: O. melanopus (Linnaeus, 1758), O. rufocyanea (Suffrian, 1847), O. duftschmidi (Redtenbacher, 1874), O. mauroi sp. nov. (northern Italy), and O. verae sp. nov. (Spain and Portugal). The two new species are described and illustrated. The nomenclature of the group is discussed in detail. Oulema rufocyanea is proved to be a validly described species different to O. duftschmidi. To fi x the nomenclatural stability of the whole group and avoid subsequent misintepretations, neotypes are designated for Crioceris melanopoda O. F. Müller, 1776; Crioceris hordei Geoffroy, 1785; and Lema cyanella var. atrata Waltl, 1835 (all conspecifi c with O. melanopus). The primary type specimens or their photographs were examined if they exist. The spelling Oulema melanopus is fixed as correct and explained. Variation in the cytochrome c oxidase (cox1) gene across specimens of all the species has been analysed. All species in the group had extremely similar haplotypes, with interspecifi c sequence similarities between 90.5–99.5 %, compared to intraspecifi c sequence similarities between 91.6–100 %. As a result, the phylogenetic relationships among species in the group were not well resolved based on cox1 sequences.