Rhamphichthys is a genus of weakly electric knifefish in the family Rhamphichthyidae, the sand knifefishes, distributed widely across South American rivers in Brazil, Colombia, Guyana, Peru, Venezuela, Argentina, Bolivia, and Ecuador. The atlas covers 7 species ranging from about 10.5 in up to a metre in length, making this one of the larger-bodied genera among the region's electric knifefishes. The genus is named for its long, narrow, downward-curving snout, an adaptation used together with a weak electric organ discharge to locate buried invertebrate prey. By day, sand knifefish typically bury themselves in sandy river-bottom substrate, emerging at night to forage.
Rhamphichthys is essentially absent from the ornamental trade; its large adult size and burrowing, sand-substrate lifestyle make it far more a subject of ichthyological and electric-fish research than an aquarium prospect, unlike smaller relatives sold as ghost or glass knifefish. Notably, every assessed species in the atlas, including the sand knifefish P. apurensis and P. rostratus, the roundnose knifefish P. hahni, and the panther sand knifefish P. pantherinus, carries a Least Concern rating, reflecting a genus that is broadly distributed across major South American river basins without evidence of significant range-wide decline.