Simple SummaryHoverflies are a diverse group (6200+ species) of two-winged flies that provide important ecosystem services (e.g., plant pollination and regulation of populations of pest insects). The hoverfly genusEumerushas caught the attention of scientists and entomology amateurs due to its high number of species worldwide (250+) and its wide range of body sizes and shapes. Nevertheless, some species show a similar overall appearance making both their separation from each other and the study of their classification/biology difficult. Thus, the aim of the present work is to update the knowledge of theEumerushoverflies in the Iberian Peninsula by assessing the diversity of theEumerus tricolorgroup under an integrative approach (i.e., combining different techniques and data sources). We found and described two new species from Spain and provided the most comprehensive identification key for all known European species of thisEumerusgroup.AbstractEumerusMeigen, 1822 is one of the largest Syrphidae genera in the Palaearctic Region, with the highest levels of taxonomic diversity found in theEumerus tricolorspecies group. Despite its high diversity, the interspecific levels of morphological variability can be low. Additionally, some species may show certain levels of intraspecific variability. Hence, species delimitation may become challenging. In this work, we assessed the diversity of theE. tricolorgroup in the Iberian Peninsula through an integrative analysis of nomenclature, morphology and the 5′ (COI-5′) and 3′ (COI-3′) end regions of the Cytochromecoxidase subunit I gene. Two new species,Eumerus ancylostylusAguado-Aranda & Ricarte sp. n. andEumerus petrarumAguado-Aranda, Nedeljković & Ricarte sp. n., were described, and their intra- and interspecific variations discussed. In addition, the first barcodes of Iberian members of theE. tricolorgroup were obtained, and the distribution ranges of all species were mapped within the study area. The systematic position of the new species is discussed based on the resulting COI-based trees. The male genitalia ofEumerus hispanicusvan der Goot, 1966 andEumerus bayardiSéguy, 1961 were studied and illustrated. A lectotype was designated forEumerus lateralis(Zetterstedt, 1819). An updated dichotomous key for all known European species of theE. tricolorgroup is provided. The egg ofE. petrarumsp. n. is also described.