Papilio is a genus in the swallowtail butterfly family, Papilionidae, as well as the only representative of the tribe Papilionini.

[2] It includes the common yellow swallowtail (Papilio machaon), which is widespread in the Northern Hemisphere and the type species of the genus, as well as a number of other well-known North American species such as the western tiger swallowtail (Papilio rutulus).

Older classifications of the swallowtails tended to use many rather small genera.

More recent classifications have been more conservative, and as a result a number of former genera are now absorbed within Papilio, such as Achillides, Eleppone, Druryia, Heraclides (giant swallowtails), Menelaides, Princeps, Pterourus (tiger swallowtails), and Sinoprinceps.

Caterpillars sequester terpenoids from their diet to produce a foul smelling oil used in defence.