Compsaraia is a genus of South American knifefish in the ghost knifefish family Apteronotidae, part of the weakly electric order Gymnotiformes. The atlas's 3 species (C. compsa, C. iara, C. samueli) range 9–13.5 in and are found in major river systems of the Amazon and Orinoco basins across Brazil, Colombia, Peru and Venezuela. Like other apteronotids, they lack a caudal fin, swim by undulating a long anal fin that runs most of the body's underside, and generate a continuous, weak electric field from an organ near the tail that they use to navigate and locate prey in dark or turbid water, and in some species to communicate with others of their kind.
Ghost knifefish in this genus are mostly of scientific rather than aquarium interest - Compsaraia species are largely nocturnal and associated with deeper river channels and rapids rather than the calmer backwaters favored by the few gymnotiforms that do reach the trade, and none of the three species here has an established common name or hobby following. All three are currently assessed Least Concern. The genus is a comparatively recent addition to the knifefish family tree, erected to separate its species from other, superficially similar long-snouted apteronotids on closer taxonomic study.