Simple SummaryEncarsia(Family Aphelinidae) is a genus of minute parasitoid wasps that target a diversity of agricultural pest insects including whiteflies and armoured scale insects. Since the genus was described in 1878, 450+ species ofEncarsiahave been described. Historically, it has been difficult to provide a subgeneric classification for the species ofEncarsia. As a result, researchers have divided the group into numerous informal species-groups. Our work uses an alignment of ribosomal DNA sequences (sequences that code for ribosomal RNA) to construct a phylogenetic tree that shows that species of the genusDirphysare correctly placed withinEncarsia. With these results, we establish theEncarsia mexicanaspecies-group (for the six species previously placed inDirphys) and describe 14 new species. We also briefly discuss morphological characters that may correspond to the relationships recovered in the molecular phylogeny. With this information, we can better understand the patterns of evolution which brought about the present diversity withinEncarsiaand provide a more accurate classification of the genus.AbstractThe genusDirphysHoward 1914syn. n.is synonymized withEncarsiaFörster, and treated as a species-group ofEncarsia, referred to henceforth as theEncarsia mexicanaspecies-group. The monophyly ofEncarsiais discussed in relation toDirphys. The new synonymy is based on phylogenetic analyses of the nuclear ribosomal 28S-D2 gene region (43 taxa, 510 bp). TheEncarsia mexicanaspecies-group is recovered as strongly monophyletic withinEncarsia.All species of theEncarsia mexicanaspecies-group are revised. The group includes six previously described species, and fourteen newly described species. All species are described (or redescribed) and illustrated. Detailed distributional data, and, where available, plant associate and host records are provided for all species.Encarsia myartsevaeKresslein and Polaszeknom. nov.is here proposed as a replacement name forEncarsia mexicanaMyartseva, now preoccupied byEncarsia mexicana(Howard). A dichotomous identification key, supplemented by an online multiple-entry key, is provided for all species.