Hycleus is a hyper-diverse genus of blister beetles including ~500 species widely distributed in the Old World, currently divided into three "sections" and into 45 "phenetic" species groups according to morphological characters. Recently the monophyly of Hycleus was questioned pointing out its paraphyly with respect to the genera Ceroctis and Paractenodia. In this study, we built a time-calibrated phylogenetic tree based on DNA sequence data from mitochondrial and nuclear genes obtained from 125 species, to understand the phylogenetic relationships among the species of this genus, to infer the biogeographic processes behind their diversification, and to assess their taxonomy and classification. Our results identified four main lineages one of which included the species belonging to Ceroctis and Paractenodia; therefore, both taxa are now referred to Hycleus as new synonyms. The three described sections of Hycleus resulted polyphyletic and are rejected, whereas several species groups represented well supported clades. Hycleus likely originated in Africa during the Early Miocene (~20 Mya), and subsequently spread in Europe and western Asia. Later, in the Late Miocene (~6 Mya) a Saharo-Sindian group branched off from the Palaearctic lineage, whereas the Oriental Region was colonized following a dispersal event through the Arabian Peninsula from the Afrotropical Region (~5 Mya).