Swallowtail may refer to:
- Swallow-tail coat, a formal tailcoat worn traditionally as part of white tie—see Tailcoat#Dress coat.
- Swallowtail butterfly, large colorful butterflies from the family Papilionidae.
- The 1996 film Swallowtail Butterfly (film), directed by Shunji Iwai, or "Swallowtail Butterfly (Ai no Uta)", the theme song for the film.
- Swallowtail (flag), a term in vexillology.