Sternopygus is a genus of glass knifefishes found in tropical and subtropical South America (south to the Río de la Plata Basin), and Panama.

They inhabit a wide range of freshwater habitats, from fast-flowing rivers to essentially static waters in floodplains, and shallow habitats to the bottom of deep rivers.

S. macrurus will even visit brackish mangrove to feed.

[1] They are medium to large knifefish, with a maximum total length of 23–140 cm (0.8–4.6 ft) depending on the exact species.

[1][2] They feed on invertebrates, small fish and fruits.