Lycaena phlaeas, the small copper, American copper, or common copper, is a butterfly of the Lycaenids or gossamer-winged butterfly family. According to Guppy and Shepard (2001), its specific name phlaeas is said to be derived either from the Greek phlego, "to burn up" or from the Latin floreo, "to flourish".

The upperside forewings are a bright orange with a dark outside edge border and with eight or nine black spots. The hindwings are dark with an orange border. Some females also have a row of blue spots inside the orange border and are known as form caeruleopunctata. The undersides are patterned in a similar way but are paler. The black spots on the forewings are outlined in yellow and the dark colouring is replaced by a pale brownish grey. The hindwings are the same brown/grey colour with small black dots and a narrow orange border. The caterpillars (larvae) are usually green, but some have a purple stripe down the middle of the back and along each side.

It is a Holarctic species, widespread and common across Europe, Asia, North America, and also found in North Africa south through to Ethiopia. It can be found almost anywhere in south/central England and Wales although never, it seems, in large numbers. Its distribution becomes more patchy in northern England, Scotland and Ireland.

In bright sun it is a very active little butterfly with the males setting up small territories which they will defend vigorously against rival males or indeed any unlucky passing insect. Even the shadow of a large bird passing overhead is enough to elicit a response. Females are pursued and mating usually occurs in vegetation.

The eggs are laid singly and conspicuously on the upperside of food plant leaves and the young caterpillar feeds on the underside of the leaf creating "windows" by leaving the upper epidermis of the leaf untouched. Pupation takes place in the leaf litter and the pupa is thought to be tended by ants. There are between two and three broods a year, fewer further north. In exceptionally good years, a fourth brood sometimes occurs in the south and adults can still be seen flying into November. The species overwinters as a caterpillar.

Depending on the habitat, common sorrel (Rumex acetosa) and sheep's sorrel (Rumex acetosella) are the two main food plants, although other docks (Rumex species) are occasionally used.

Lycaena phlaeas belongs to the subgenus Lycaena and is the type-species of genus Lycaena. The species is in turn divided into several subspecies, although many probably lack reason to be named, and others may merit an elevation of rank to be considered autonomous species: - L. p. hibernica Goodson, 1948 — Republic of Ireland, Northern Ireland - L. p. eleus Fabricius, 1798 — England, Wales, Scotland - L. p. phlaeas Linnaeus, 1761 — Europe, western Siberia, Caucasus, South Caucasus (type locality = Sweden) - L. p. polaris Courvoisier, 1911 — northern Ural Mountains, northern Siberia, Chukotka Peninsula (Russia) - L. p. kamtschatica Gorbunov, 1994 — Kamchatka Peninsula (Russia) - L. p. ganalica Gorbunov, 1995 — Kamchatka Peninsula (Russia) - L. p. daimio (Seitz, [1909]) — south Kurile Islands, Sakhalin (Russian islands) - L. p. gonpaensis (Yoshino, [2019]) — North Yunnan, China - L. p. hypophlaeas (Boisduval, 1852) — N California Sierra Nevada Mts (Type location) and White Mts., Altai Mountains, southern Siberia, Amur (Russia–NW China border region), northern Ussuri (adjacent to Amur) - L. p. chinensis (Felder, 1862) — southern Ussuri - L. p. oxiana (Grum-Grshimailo, 1890) — Kopet Dag mountains, Alai Mountains, Ghissar-Darvaz, Tian Shan mountains - L. p. comedarum (Grum-Grshimailo, 1890) — eastern Pamir Mountains - L. p. stygiana Butler, 1880 — western Pamir Mountains - L. p. shima Gabriel, 1954 — Arabia - Lycanea phlaeas pseudophlaeas (Lucas, 1866) — Ethiopia, Uganda - L. p. ethiopica (Poulton, 1922) — Ruwenzori Mountains (SW Uganda) - L. p. abbottii (Holland, 1892) — Kenya, Tanzania, Malawi - L. p. flavens (Ford, 1924) — Tibet - L. p. coccinea (Ford, 1924) - L. p. americana (Morris, 1862) — Nova Scotia and W. to Minnesota, and S. to: Virginia, Montane N Georgia, Missouri, Kansas, N Dakota. - L. p. arethusa (Dod, 1907) — Alberta - L. p. arctodon Ferris, 1974 — Montana - L. p. feildeni (McLachlan, 1878) — Ellesmere - L. p. alpestris Emmel & Pratt, 1998 — California