The Nearctic members of the genus Platycheirus Lepeletier and Serville are revised. Five species, Platycheirus alpigenus Nielsen and Barkalov, Platycheirus brunnifrons Nielsen, Platycheirus clausseni Nielsen, Platycheirus speighti Doczkal, Stuke, and Goeldlin, and Platycheirus splendidus Rotheray, are newly recorded for the Nearctic Region, while three species, Platycheirus sp. trichopus, Platycheirus sp. “hyperboreus dark form” and Platycheirus n. sp. “perpallidus1” are new manuscript names. Females of 42 species are described for the first time. The genus Pyrophaena Schiner is resurrected. The genus Tuberculanostoma Fluke is synonymized with Platycheirus. An illustrated key to all 73 males and 52 females of Platycheirus and the males and females of the 3 species of Pyrophaena occurring in the Nearctic region is provided. Morphological and combined morphological/molecular COI phylogenetic analyses of the Platycheirus albimanus group are presented, as well as a molecular analysis of all available Platycheirus COI sequences. The species groups within Platycheirus are redefined based on these analyses. / NSERC-CANPOLIN