Earwigs make up the insect order Dermaptera. With about 2,000 species in 12 families, they are one of the smaller insect orders. Earwigs have characteristic cerci, a pair of forceps-like pincers on their abdomen, and membranous wings folded underneath short, rarely used forewings, hence the scientific order name, "skin wings". Some groups are tiny parasites on mammals and lack the typical pincers. Earwigs are found on all continents except Antarctica.

Earwigs are mostly nocturnal and often hide in small, moist crevices during the day, and are active at night, feeding on a wide variety of insects and plants. Damage to foliage, flowers, and various crops is commonly blamed on earwigs, especially the common earwig Forficula auricularia.

Earwigs have five molts in the year before they become adults. Many earwig species display maternal care, which is uncommon among insects. Female earwigs may care for their eggs; the ones that do will continue to watch over nymphs until their second molt. As the nymphs molt, sexual dimorphism such as differences in pincer shapes begins to show.

Extant Dermaptera belong to the suborder Neodermaptera, which first appeared during the Cretaceous. Some earwig specimen fossils are placed with extinct suborders Archidermaptera or Eodermaptera, the former dating to the Late Triassic and the latter to the Middle Jurassic. Dermaptera belongs to the major grouping Polyneoptera, and are amongst the earliest diverging members of the group, alongside angel insects (Zoraptera), and stoneflies (Plecoptera), but the exact relationship among the three groups is uncertain.

The scientific name for the order, Dermaptera, is Greek in origin, stemming from the words derma, meaning 'skin', and pteron (plural ptera), meaning 'wing'. It was coined by Charles De Geer in 1773. The common term, earwig, is derived from the Old English ēare, which means 'ear', and wicga, which means 'insect', or literally, 'beetle'. Entomologists suggest that the origin of the name is a reference to the appearance of the hindwings, which are unique and distinctive among insects, and resemble a human ear when unfolded. The name is more popularly thought to be related to the old wives' tale that earwigs burrowed into the brains of humans through the ear and laid their eggs there. Earwigs are not known to purposefully climb into ear canals, but there has been at least one anecdotal report of earwigs being found in the ear.

Earwigs are abundant and can be found throughout the Americas and Eurasia. The common earwig was introduced into North America in 1907 from Europe, but tends to be more common in the southern and southwestern parts of the United States. The only native species of earwig found in the north of the United States is the spine-tailed earwig (Doru aculeatum), found as far north as Canada, where it hides in the leaf axils of emerging plants in southern Ontario wetlands. However, other families can be found in North America, including Forficulidae (Doru and Forficula being found there), Spongiphoridae, Anisolabididae, and Labiduridae.

Few earwigs survive winter outdoors in cold climates. They can be found in tight crevices in woodland, fields and gardens. Out of about 1,800 species, about 25 occur in North America, 45 in Europe (including 7 in Great Britain), and 60 in Australia.

Most earwigs are flattened (which allows them to fit inside tight crevices, such as under bark) with an elongated body generally 7–50 millimetres (1⁄4–2 in) long. The largest extant species is the Australian giant earwig (Titanolabis colossea) which is approximately 50 mm (2 in) long, while the possibly extinct (declared extinct in 2014) Saint Helena earwig (Labidura herculeana) reached 78 mm (3+1⁄16 in). Earwigs are characterized by the cerci, or the pair of forceps-like pincers on their abdomen; male earwigs generally have more curved pincers than females. These pincers are used to capture prey, defend themselves and fold their wings under the short tegmina. The antennae are thread-like with at least 10 segments.