A new genus and species of predaceous water bugs, Triassonepa solensis n. gen. n. sp., is described from the Triassic Cow Branch Formation of Virginia and North Carolina (USA) based on ~36 adult specimens and 51 nymphs. This species is the oldest known member of the extant family Belostomatidae. It is placed in a new genus based on the unique structure of the raptorial foreleg, in which the tarsus is elongate and opposed to the tibia femur. The fossil record of this family is reviewed and the paleoenvironmental implications of the species assemblage preserved in the Cow Branch Formation are discussed.