The mecopterans are a small order of holometabolous, winged insects.

The typical mecopteran has an elongate body, six long legs, two pairs of transparent, brown-spotted wings, and a very long, snout-like head with chewing mouth parts. This snout is characteristic for the order. The males of the largest mecopterid family, the scorpionflies (Panorpidae), have enlarged genitalia that are held above the abdomen, resembling the stinger of a scorpion. The small, boreal and alpine family Boreidae (sometimes called snow scorpionflies) contain small, wingless species that are active on snow during the winter. It is believed that this group has given rise to the fleas (Siphonaptera).