Chenopodium album is a fast-growing annual plant in the flowering plant family Amaranthaceae. Though cultivated in some regions, the plant is elsewhere considered a weed. Common names include lamb's quarters, melde, goosefoot, wild spinach and fat-hen, though several are also applied to other species of the genus Chenopodium, for which reason it is often distinguished as white goosefoot.

It tends to grow upright at first, reaching heights of 10–150 centimetres (4–59 in), rarely to 3 m); it then typically becomes recumbent after flowering (due to the weight of the foliage and seeds) unless supported by other plants. The leaves are alternate and varied in appearance. The first leaves, near the base of the plant, are toothed and roughly diamond-shaped, 3–7 cm long and 3–6 cm broad. The leaves on the upper part of the flowering stems are entire and lanceolate-rhomboid, 1–5 cm long and 0.4–2 cm broad; they are waxy-coated, unwettable and mealy in appearance, with a whitish coat on the underside. The small flowers are radially symmetrical and grow in small cymes on a dense branched inflorescence 10–40 cm long. Further, the flowers are bisexual and female, with five tepals which are mealy on outer surface, and shortly united at the base. There are five stamens.

Poisonous black nightshade looks similar to this species when young, but the leaves of C. album have a white mealy texture and its axils have a red streak.

Chenopodium album has a complex taxonomy and has been divided into numerous microspecies, subspecies and varieties, but it is difficult to differentiate between them. The following varieties are accepted by Plants of the World Online:

Its native range is obscure due to extensive cultivation, but includes most of Europe, from where Carl Linnaeus described the species in 1753. Plants native to eastern Asia are included under C. album, but often differ from European specimens. According to Plants of the World Online, the species' natural distribution includes temperate Eurasia from western Europe to China and the Russian Far East, the Indian subcontinent, North Africa, Ethiopia, and the eastern and central United States.

It is widely naturalized elsewhere, such as in Africa, Australasia, North America, and Oceania, and now occurs almost everywhere (except Antarctica) in soils rich in nitrogen, especially on wasteland.^{[citation needed]}

The species are cultivated as a grain or vegetable crop (such as in lieu of spinach), as well as animal feed in Asia and Africa, whereas in Europe and North America, it is commonly regarded as a weed in places such as potato fields, while in Australia it is naturalised in all states and regarded as an environmental weed in New South Wales, Victoria, Western Australia and the Northern Territory. While var. album is considered invasive in some regions of the U.S., var. missouriense is native.

It is one of the more robust and competitive weeds, exceptionally capable of colonizing new areas. It may produce up to 50 million seeds per hectare, its seeds remain viable 30 to 40 years in the soil, and it exhibits high phenotype plasticity, modifying its growth form for the conditions it is in. It may be controlled by dark tillage, rotary hoeing, or flaming when the plants are small. Crop rotation of small grains will suppress an infestation. It is easily controlled with a number of pre-emergence herbicides. Its pollen may contribute to hay fever-like allergies.