The classification of New World martins (Progne) has a convoluted history because taxonomists have relied on plumage traits that vary continuously across populations. We estimated the phylogeny of Progne by analyzing mitochondrial cytochrome b DNA sequences of 27 individuals of eight of the nine species (10 subspecies) and nuclear β-fibrinogen intron 7 sequences of 20 individuals of six species (8 subspecies). The Brown-chested Martin (P. tapera) is sister to other Progne species. The Middle American taxa—Sinaloa Martin (P. sinaloae), Cuban Martin (P. cryptoleuca), Caribbean Martin (P. dominicensis), and Central American populations of Gray-breasted Martin (P. chalybea)—form a well supported clade. This group is distinct from Purple Martin (P. subis), which has no particularly close relatives. All four Middle American taxa appear to be good species, although Cuban and Caribbean martins could be merged in view of their similar plumage and low genetic divergence (1.2%). Two of the South American taxa, the Peruvian Martin (P. murphyi) and Southern Martin (P. elegans), are also distinct species. We did not examine the Galapagos Martin (P. modesta) for lack of DNA, but it is likely to be a good species as well. An unexpected result of the study was that Gray-breasted Martin appears polyphyletic; its South American populations are closer to the Southern Martin than to its Central American populations.