Phalloceros titthos, the breast toothcarp, is a species of poeciliid fish native to Brazil.
Phalloceros titthos is found in the coastal drainages flowing into the Baia de Guaratuba and the Baia de Paranaguá in Paraná, Brazil.
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 in Greek for a woman's breast or animal's teat, referring to the small papillae at the mandibular symphysis of large adult females.