The Neotropical genus Syntomoneurum Becker is revised. The genus is defined within the subfamily Dolichopodinae on the basis of the possession of a strong basiventral seta on the fore femur, a single notopleural seta, and very reduced pulvilli on the midleg and hindleg in both sexes. Males also possess a cluster of 2-3 strong setae on both the fore femur and mid coxa. One new species, Syntomoneurum giganteum Brooks is described and the three previously known species (S. alatum Becker, S. anale Parent, S. beckeri Parent) are redescribed. A lectotype is designated for S. alatum. A key to the species is provided. Evidence supporting the placement of Syntomoneurum in the subfamily Dolichopodinae near Tachytrechus Haliday is discussed.