Papilio sosia, the medium green-banded swallowtail, is a butterfly of the family Papilionidae.

Forewing above in cellules 1 b—8 with distinct, small, usually double submarginal dots, but beneath without large submarginal spots; the median band formed almost as in nireus, though the spot in cellule 2 covers the base of the cellule, but is more produced anally than the spot in 1 c, which does not reach the cell.

[4] The median band is straight and regular and never less than 1 cm in cell lb of the forewing, nearly always much wider.

Subspecies include: Papilio sosia belongs to a clade called the nireus species group with 15 members.

The pattern is black with green or blue bands and spots and the butterflies, although called swallowtails, they lack tails with the exception of Papilio charopus and Papilio hornimani.