We performed the first, comprehensive molecular phylogenetic analysis of Vespoidea. The data were derived from four nuclear genes (wingless, long-wavelength rhodopsin, the F2 copy of elongation factor-1a, and the D2-D3 region of the ribosomal RNA gene 28S) for 52 species of Vespoidea and multiple representatives of Chrysidoidea (Plumariidae, Chrysididae, and Bethylidae) and Apoidea (Sphecidae, Crabronidae, Apidae, Colletidae, and Halictidae) as outgroups. The combined genetic matrix was analyzed using Bayesian methods, which produced high posterior probabilities for most nodes and demonstrated that Apoidea is nested within Vespoidea. The analysis also suggests interesting relationships within Vespoidea, such as Vespidae sister to Rhopalosomatidae, and that Mutillidae, Bradynobaenidae and Tiphiidae are also paraphyletic.