Swartzia (ca. 180 spp.) is a characteristic and diverse element of neotropical rainforest tree communities. As such, it has been identified as a focal group in studies of evolutionary diversification and community assembly in rainforests. However, progress is impeded by the lack of a phylogenetic hypothesis for the genus and its close relatives, which together constitute the descendents of one of the first branches of the papilionoid phylogeny. Here we present a molecular phylogenetic study with extensive sampling of species of Swartzia and with complete sampling of genera of the "swartzioid" clade. The results, based on analysis of chloroplast (atpB-rbcL, trnL intron, and trnL-F) and nuclear (AAT1 and ITS) DNA sequences, add substantially to our understanding of relationships within this diverse group and call for taxonomic changes, particularly within Swartzia. The monophyly of a redefined Swartzia is weakly to moderately supported. Within Swartzia, the analyses identify 11 nonoverlapping subclades, few of which correspond exactly to previously published taxa. The analyses support the recent segregations of Bobgunnia from Swartzia and of Trischidium from Bocoa, as well as the resurrection of the monospecific genus Fairchildia. The analyses identify a "core swartzioid" clade comprising the remainder of Swartzia, Bocoa, and Candolleodendron.