Swallowtail butterflies are large, colorful butterflies that form the family Papilionidae. There are over 550 species, and though the majority are tropical, members of the family are found on all continents except Antarctica. The family includes the largest butterflies in the world, the birdwing butterflies of Australia (genus Ornithoptera).

Swallowtails differ from all other butterflies in a number of anatomical traits. Most notably, their caterpillars possess a unique organ behind their heads, called the osmeterium. Normally hidden, this forked structure can be everted when the caterpillar is threatened, or forced out with a gentle squeeze, and emits smelly secretions containing terpenes. The adults are often tailed like the forked tail of some swallows, giving the insect its name.