Parides ascanius, the Fluminense swallowtail, is a species of butterfly in the family Papilionidae.

It is endemic to Brazil where it is confined to the municipalities of Atafona (São João da Barra) and Itaguaí.

A full description is provided by Rothschild, W. and Jordan, K. (1906)[3] Parides ascanius larvae are found from October to April, feeding only on Aristolochia macroura in its preferred wetland habitats.

The common name, "Fluminense", is the demonym for residents of the state of Rio de Janeiro, Brazil.

Biology and ecology of Parides ascanius (Cramer, 1775) (Lep., Papilionidae), a primitive butterfly threatened with extinction Atala 10.