The genus Polistes is one of the most species-rich and widely distributed groups of social wasps and a model taxon for studies of social behavior. Almost half the Polistes world fauna occurs in the New World, but their classification has been unstable due in part to the scarcity of phylogenetic studies. We investigated the phylogeny of the New World Polistes by combining a previously existing molecular dataset with a new morphological and behavioral matrix for 90 of the 93 New World species. All analyses support a single origin for the New World Polistes. All five traditionally defined New World subgenera (Aphanilopterus, Epicnemius, Fuscopolistes, Onerarius, and Palisotius) were monophyletic, but the relationships among them varied across datasets. Our results, with an expanded phenotypic dataset, improved taxonomic sampling, and enhanced clade support relative to previous studies, strongly support a classification based on five subgenera, which are all diagnosable groups supported by clear morphological synapomorphies. Hence, we propose the revalidation of previously proposed subgenera; we provide a taxonomic account of each subgenus and an identification key to all species of New World Polistes.