Chenopodium is a genus of numerous species of perennial or annual herbaceous flowering plants known as the goosefoot, which occur almost anywhere in the world. It is placed in the family Amaranthaceae in the APG II system; older classification systems, notably the widely used Cronquist system, separate it and its relatives as Chenopodiaceae, but this leaves the rest of the Amaranthaceae polyphyletic. However, among the Amaranthaceae, the genus Chenopodium is the namesake member of the subfamily Chenopodioideae.

The species of Chenopodium (s.str., description according to Fuentes et al. 2012) are annual or perennial herbs, shrubs or small trees. They generally rely on alkaline soil. They are nonaromatic, but sometimes fetid (foul-smelling). The young stems and leaves are often densely covered by vesicular globose hairs, thus looking farinose. Characteristically, these trichomes persist, collapsing later and becoming cup-shaped. The branched stems grow erect, ascending, prostrate or scrambling. Lateral branches are alternate (the lowermost ones can be nearly opposite). The alternate or opposite leaves are petiolate. Their thin or slightly fleshy leaf blade is linear, rhombic or triangular-hastate, with entire or dentate or lobed margins.

Inflorescences are standing terminal and lateral. They consist of spicately or paniculately arranged glomerules of flowers. Plants are monoecious (rarely dioecious). In monoecious plants flowers are dimorphic or pistillate. Flowers consist of (4–) 5 perianth segments connate, basally (at the base) or close to the middle, usually membranous margined and with a roundish to keeled back; almost always 5 stamens, and one ovary with 2 stigmas.

In fruit, perianth segments become sometimes coloured, but mostly keep unchanged, somewhat closing over or spreading from the fruit. The pericarp is membranous or sometimes succulent, adherent to or loosely covering the seed. The horizontally oriented seeds are depressed-globular to lenticular, with rounded to subacute margin. The black seed coat is almost smooth to finely striate, rugulose or pitted.

The genus Chenopodium was described by Carl Linnaeus in 1753 (In: Species Plantarum, Vol. 1, p. 218–222). Type species is Chenopodium album. This generic name is derived from the particular shape of the leaf, which is similar to a goose's foot: from Greek χήν (chen), "goose" and πούς (pous), "foot" or ποδίον (podion), "little foot".

In its traditional circumscription, Chenopodium comprised about 170 species. Phylogenetic research revealed, that the genus was highly polyphyletic and did not reflect how species were naturally related. Therefore, a new classification was necessary. Mosyakin & Clemants (2002, 2008) separated the glandular species as genus Dysphania (which includes epazote) and Teloxys in tribe Dysphanieae. Fuentes-Bazan et al. (2012) separated many species to genera Blitum (in tribe Anserineae), Chenopodiastrum, Lipandra, and Oxybasis (like Chenopodium in tribe Atripliceae). They included Rhagodia and Einadia in Chenopodium.

132 species are currently accepted.

Certain species grow in large thickets, providing cover for small animals. Goosefoot foliage is used as food by the caterpillars of certain Lepidoptera.^{[citation needed]} The seeds are eaten by many birds, such as the yellowhammer (Emberiza citrinella) of Europe or the white-winged fairy-wren (Malurus leucopterus) of Australia.^{[citation needed]} Goosefoot pathogens include the positive-sense ssRNA viruses – apple stem grooving virus, sowbane mosaic virus and tobacco necrosis virus.^{[citation needed]}