The Noctuidae, commonly known as noctuid moths or owlet moths, and their caterpillars as cutworms or armyworms, are a family of moths. Taxonomically, they are considered the most difficult family in the superfamily Noctuoidea because the classification of many of the clades is constantly changing with new research, along with that of other families of the Noctuoidea. It was considered the largest family in Lepidoptera for a long time, but after regrouping Lymantriinae, Catocalinae and Calpinae within the family Erebidae, the latter holds this title now. Currently, Noctuidae is the second largest family in Noctuoidea, with about 1,089 genera and 11,772 species. This classification is still unsettled, as more changes continue to appear between Noctuidae and Erebidae.

 Adult: Most noctuid adults have wings with a variety of shades of brown, grey, and other varied shades and colours but some subfamilies, such as Acronictinae and Agaristinae, are very brightly coloured, especially those from tropical regions (e.g. Baorisa hieroglyphica). They are characterised by a structure in the metathorax called the nodular sclerite or epaulette, which separates the tympanum and the conjunctiva in the tympanal organ. It functions to keep parasites (Acari) out of the tympanal cavity. Another characteristic in this group is trifine hindwing venation, by reduction or absence of the second medial vein (M2).

Markings present on the wings of noctuid adults can be helpful in distinguishing species. From the basal location to the outer edge (proximal to distal) on the forewing, there is a horizontally oriented claviform (club-shaped) stigma located posterior to a discal (round) stigma. These are followed distally by a reniform (kidney-shaped) stigma, whose exact shape may vary, but is found on the distal edge of the forewing´s cell. It is often not possible to discern all of the stigmata on all specimens or species. Crossbands or crosslines may be present, oriented longitudinally from the leading to the trailing edge of the wing.

Larva: Commonly green or brown; some species present bright colours, such as the camphorweed cucullia moth (Cucullia alfarata). Most are pudgy and smooth with rounded short heads and few setae, but there are some exceptions in some subfamilies (e.g. Acronictinae and Pantheinae).

The pupae range from shiny brown to dark brown. When they newly pupate they are bright brownish orange, but after a few days start to get darker.

The eggs vary in colour, but all have a spherical shape.

Etymology: The word Noctuidae is derived from the name of the type genus Noctua, which is the Latin name for the little owl, and the patronymic suffix -idae used typically to form taxonomic family names in animals.

The common name "owlet" originally means a small or young owl. The names "armyworms" and "cutworms" are based on the behaviour of the larvae of this group, which can occur in destructive swarms and cut the stems of plants.

Distribution and diversity: This family is cosmopolitan and can be found worldwide except in the Antarctic region. Some species, such as the setaceous Hebrew character (Xestia c-nigrum), can be found in the Arctic Circle, specifically in the Yukon territory of western Canada, with an elevation 1,702 m above sea level, where the temperature fluctuates between 23/-25 °C (73/-13 °F). Many species of dart moths have been recorded in elevations as high as 4,000 m above sea level (e.g. Xestia elisabetha).
Among the places where the number of species has been counted are North America and northern Mexico, with about 2,522 species. 1,576 species are found in Europe, while the other species are distributed worldwide.

Mutualism: Members of Noctuidae, like other butterflies and moths, perform an important role in plant pollination. Some species have developed a stronger connection with their host plants. For example, the lychnis moth (Hadena bicruris) has a strange mutualistic relationship with pink plants or carnation plants (Caryophyllaceae), in that larvae feed on the plant while the adults pollinate the flowers.

Food guilds: Herbivory: Caterpillars of most Noctuidae feed on plants; some feed on poisonous plants and are unaffected by their chemical defences; for example, the splendid brocade moth (Lacanobia splendens) feeds on cowbane (Cicuta virosa), a plant that is notoriously toxic to vertebrates.

Predation and cannibalism: During the larval stage, some cutworms readily feed on other insects. One such species is the shivering pinion (Lithophane querquera), whose larvae commonly feed on other lepidopteran larvae. Moreover, many noctuid larvae, such as those of the fall armyworm (Spodoptera frugiperda) and of genera such as Heliothis and Helicoverpa, aggressively eat their siblings and often other species of caterpillar.

Nectarivory and puddling: Like many Lepidoptera, many species of adult Noctuidae visit flowers for their nectar. They also seek other liquid food resources such as plant juices, honeydew, dung, urea and mud, among others.

As is common in members of the order Lepidoptera, courtship in many Noctuidae includes a set of movements in which the female evaluates the male´s reproductive fitness.

Most noctuid moths produce pheromones that attract the opposite sex. Female pheromones that attract males occur widely and have long been studied, but the study of male pheromones has further to go.

Reproduction: Noctuid moths commonly begin the reproductive season from spring to fall, and mostly are multivoltine, such as the eastern panthea moth (Panthea furcilla), which reproduces over the year. Nevertheless, some species have just one brood of offspring (univoltine); among the best known is the lesser yellow underwing (Noctua comes).

Defence: This group has a wide range of both chemical and physical defence. Among the chemical defences three types stand out. First, the pyrrolizidine alkaloid sequestration usually present in Arctiinae is also found in a few species of noctuids, including the Spanish moth (Xanthopastis timais). Another chemical defence is formic acid production, which was thought to be present only in Notodontidae, but later was found in caterpillars of Trachosea champa. Finally, the last type of chemical defence is regurgitation of plant compounds, often used by many insects, but the cabbage palm caterpillar (Litoprosopus futilis) produces a toxin called toluquinone that deters predators.

On the other hand, the main physical defence in caterpillars and adults alike is mimicry. Most noctuid moths have drab colours with a variety of patterns suitable to camouflage their bodies. The second physical defence consists in thousands of secondary setae that surround the body. The subfamilies that present this mechanism are Pantheinae and Acronictinae. The third is aposematism, represented by species of Cucullinae. Finally, all adults have another mechanism for defence, a tympanal organ available to detect the echolocation produced by bats, so the moths can avoid them.

Human importance: Agriculture: Many species are considered agricultural problems around the world. Their larvae are typically known as "cutworms" or "armyworms" due to swarms that destroy crops, orchards and gardens every year. The scarce bordered straw Helicoverpa armigera produces losses in agriculture every year that exceed US$2 billion. Additionally, the variegated cutworm (Peridroma saucia) is described by many as one of the most damaging pests to vegetables.

In West Africa, species including Busseola fusca, Heliocheilus albipunctella, Sesamia calamistis, Helicoverpa armigera, and Spodoptera exempta are major pests of staple crops such as pearl millet, sorghum, and maize.

Systematics: Since molecular analysis began to play a larger role in systematics, the structure of many Lepidoptera groups has been changing and Noctuidae is not an exception. Most recent studies have shown that Noctuidae sensu stricto is a monophyletic group, mainly based on trifine venation. Some clades within Noctuidae sensu lato have yet to be studied. This taxonomic division represents the subfamilies, tribes and subtribes considered so far.

Family Noctuidae Latreille, 1809
: Subfamily Acontiinae Guenée, 1841
:: Tribe Acontiini Guenée, 1841
:: Tribe Armadini
:: Tribe Chamaecleini
: Subfamily Acronictinae Harris, 1841
: Subfamily Aediinae
: Subfamily Agaristinae Boisduval, 1833
: Subfamily Amphipyrinae Guenée, 1837
:: Tribe Amphipyrini Guenée, 1837
:: Tribe Psaphidini Grote, 1896
::: Subtribe Feraliina Poole, 1995
::: Subtribe Nocloina Poole, 1995
::: Subtribe Psaphidina Grote, 1896
::: Subtribe Triocnemidina Poole, 1995
: Subfamily Bagisarinae Crumb, 1956
: Subfamily Balsinae Grote, 1896
: Subfamily Bryophilinae Guenée, 1852
: Subfamily Cobubathinae Wagner & Keegan, 2021
: Subfamily Condicinae Poole, 1995
:: Tribe Condicini Poole, 1995
:: Tribe Leuconyctini Poole, 1995
: Subfamily Cropiinae Keegan & Wagner, 2021
: Subfamily Cuculliinae Herrich-Schäffer, 1850
: Subfamily Dilobinae
: Subfamily Dyopsinae
: Subfamily Eriopinae Herrich-Schäffer, 1851
: Subfamily Eucocytiinae
: Subfamily Eustrotiinae Grote, 1882
: Subfamily Grotellinae
: Subfamily Heliothinae Boisduval, 1828
: Subfamily Metoponiinae Herrich-Schäffer, 1851
:: Tribe Cydosiini Kitching & Rawlins, 1998
: Subfamily Noctuinae Latreille, 1809
:: Tribe Actinotiini Beck, 1996
:: Tribe Apameini Guenée, 1841
:: Tribe Arzamini Grote, 1883
:: Tribe Caradrinini Boisduval, 1840
::: Subtribe Athetiina Fibiger & Lafontaine, 2005
::: Subtribe Caradrinina Boisduval, 1840
:: Tribe Dypterygiini Forbes, 1954
:: Tribe Elaphriini Beck, 1996
:: Tribe Episemini
:: Tribe Eriopygini Fibiger & Lafontaine, 2005
:: Tribe Glottulini Guenée, 1852
:: Tribe Hadenini Guenée, 1837
:: Tribe Leucaniini Guenée, 1837
:: Tribe Noctuini Latreille, 1809
::: Subtribe Agrotina Harris, 1841
::: Subtribe Axyliina
::: Subtribe Noctuina Latreille, 1809
:: Tribe Orthosiini Guenée, 1837
:: Tribe Phlogophorini Hampson, 1918
:: Tribe Phosphilini Poole, 1995
:: Tribe Prodeniini Forbes, 1954
:: Tribe Pseudeustrotiini Beck, 1996
:: Tribe Tholerini Beck, 1996
:: Tribe Xylenini Guenée, 1837
::: Subtribe Antitypina Forbes & Franclemont, 1954
::: Subtribe Cosmiina Guenée, 1852
::: Subtribe Ufeina Crumb, 1956
::: Subtribe Xylenina Guenée, 1837
: Subfamily Oncocnemidinae Forbes & Franclemont, 1954
: Subfamily Pantheinae Smith, 1898
: Subfamily Plusiinae Boisduval, 1828
:: Tribe Abrostolini Eichlin & Cunningham, 1978
:: Tribe Argyrogrammatini Eichlin & Cunningham, 1978
:: Tribe Plusiini Boisduval, 1828
::: Subtribe Autoplusiina Kitching, 1987
::: Subtribe Euchalciina Chou & Lu, 1979
::: Subtribe Plusiina Boisduval, 1828
: Subfamily Raphiinae
: Subfamily Stiriinae
:: Tribe Annaphilini
:: Tribe Stiriini Grote, 1882
::: Subtribe Annaphilina Mustelin, 2006
::: Subtribe Azeniina Poole, 1995
::: Subtribe Grotellina Poole, 1995
::: Subtribe Stiriina Grote, 1882

Genera with intervening taxonomy not available include:

• Alastria
• Epilitha
• Fabula
• Lanatopyga
• Lenisa
• Neoligia
• Orohadena
• Orthomoia
• Protapamea
• Proxenus
• Pseudluperina