Fungi in the order Laboulbeniales (Ascomycota, Laboulbeniomycetes) are obligate, microscopic ectoparasites of arthropods. These fungi, unlike their close relatives, never form hyphae. Instead, they produce a three-dimensional thallus that consists of several hundred to a thousand vegetative cells derived from a two-celled ascospore by determinate mitotic divisions. Of 2,325 described species, 80 % are known from beetles (Coleoptera). Hesperomyces is a genus of 11 species associated with ladybirds (Coleoptera, Coccinellidae) and false skin beetles (Biphyllidae). One species, Hesperomyces virescens, is known from all continents except Australia and Antarctica, and has been reported on 30 ladybird hosts in 20 genera. Previous work, based on geometric morphometrics, molecular phylogeny, sequence-based species delimitation methods, and host information, pointed out that He. virescens is a complex of multiple species segregated by host. Here, we formally describe the most recorded species in the complex, Hesperomyces harmoniae—parasite of the harlequin ladybird Harmonia axyridis, a globally invasive species. Using DNA isolates of Hesperomyces from multiple host species, including the host on which He. virescens was originally described (Chilocorus stigma), we found that He. harmoniae forms a single clade in our phylogenetic reconstruction of a two-locus ribosomal dataset. Hesperomyces harmoniae is currently known from five continents and 31 countries: Canada, El Salvador, Mexico, the USA (North America); Argentina, Colombia, Ecuador (South America); Austria, Belgium, Bulgaria, Croatia, Czech Republic, France, Germany, Greece, Hungary, Italy, Luxembourg, Montenegro, The Netherlands, Poland, Romania, Russia, Serbia, Slovakia, Switzerland, the UK (Europe); South Africa (Africa); China, Japan, and Turkey (Asia).