Phalloceros harpagos, the ellipse spot toothcarp, is a species of poeciliid fish native to Brazil.
Phalloceros harpagos is found in South America and is found in the Rio Paraná-Paraguay basin and also the coastal drainages from rio Itaboapana to the rio Araranguá.
The females of this species grow to a total length of , while males remain smaller at . .
The fish live in tropical freshwater; and are benthopelagic.
The fish is named is from Greek for hook, referring to the small and simple hook in gonopodial appendix.