The superfamily Platygastroidea (Hymenoptera: Proctotrupomorpha) is a diverse group of parasitoid wasps that attack nine orders of insects as well as spiders. They appear to show a clear pattern of host group specificity among genera. A robust phylogeny is essential to understanding the monophyly of and relationships among lower level groups and the pattern of the shifts among host groups. We conducted phylogenetic analyses of Platygastroidea based on four molecular markers (18S, 28S, COI, and wingless) combined with 119 morphological characters, and a phylogenomic analysis of a subset of taxa based on 4,371 single-copy, protein-coding genes. The four-gene and morphological analyses robustly recovered some well-established groups, e.g., Platygastridae (in its traditional sense), Scelionini, Teleasinae and Telenominae, as well as some novel patterns of relationship. The ground-plan host for the superfamily are the eggs of Orthoptera, with possible parallel shifts to attack hosts in the Coleoptera, Diptera, Hemiptera and Mantodea. The basal relationships for the superfamily as well as relationships among genera traditionally classified in the scelionine tribes Baryconini, Calliscelionini and Psilanteridini were not supported. The phylogenomic analysis of representative basal taxa recovered a clear pattern of relationships with maximal bootstrap support. Based on the combination of these two approaches, we present a revised classification for Platygastroidea and recognize the following eight families: Geoscelionidae stat. rev., Janzenellidae fam. nov., Neuroscelionidae fam. nov., Nixoniidae stat. rev., Platygastridae stat. rev., Proterosceliopsidae†, Scelionidae stat. rev. and Sparasionidae stat. rev.