The butterfly family that includes swallowtail butterflies is Papilionidae.
Papilionidae contains the familiar swallowtails and birdwings, including the Old World swallowtail, the common lime, and the giant swallowtail. Many members have tails on their hindwings, although not every species has an equally prominent tail.
Papilionid caterpillars often possess an eversible, forked organ called an osmeterium. It can release defensive chemicals when the larva is disturbed. This feature helps distinguish many swallowtail caterpillars from larvae in other butterfly families.
Papilionidae is a worldwide family, with especially high diversity in tropical regions. It should not be confused with Pieridae, the family containing whites and sulphurs, or with Hesperiidae, the skipper family.