It is native to Europe, Asia and parts of Africa, where it grows on bare mud in brackish hollows in coastal grassland, inland salt steppes and salty deserts.

This strict reliance on flower structure declined with time, however, and it has until recently been known as Chenopodium chenopodioides, the name assigned to it by Paul Aellen in 1933.

However, in 2012, an analysis of the relationships of the many species in the Chenopodioideae by Susy Fuentes-Bazan and colleagues resulted in its reassignment to the new genus Oxybasis, along with red goosefoot and some related plants.

[6][7] A large number of other synonyms have been coined over the years, most notably Blitum botryoides (by Solomon Drejer in 1877) and B. crassifolium (by Heinrich Reichenbach in 1832).

[3][2] Saltmarsh goosefoot is native to southern Europe, Asia and parts of North Africa, and widely established throughout the Americas.

[12] In western north America it is well established in the Rocky Mountains, from British Columbia to California, where it grows in sagebrush desert vegetation, usually on roadsides.

[6] In France, Oxybaside faux chénopode occurs mainly around the coast and has a status of LC (Least Concern) in Corsica and the southern départements, but it is considered VU (Vulnerable) in the Nord-Pas-de-Calais and CR (critically rare) in Picardie.

[16] It is considered to be rare in Italy, where it is distributed around the coast of the mainland, Sicily and Sardinia, but is restricted by the lack of suitable habitat.

[21] The Global Biodiversity Information Forum map shows saltmarsh goosefoot extending across the central steppe of Asia as far as eastern Siberia.

It is typically found in shallow depressions, where winter flooding lasts into the spring, creating patches of bare ground.

Under the EUNIS habitat classification system, saltmarsh goosefoot is a characteristic plant of the Pannonic salt steppes of south-east Europe, and specifically of the salty E6.2131 Puccinellia distans hollows that are found in this type of grassland.

In this inland vegetation, it is evaporation of surface water in dry summers that creates the brackish conditions, rather than the influence of the sea, and the salts are mainly carbonates and sulphates rather than chlorides.

It is found on sandy, almost bare soils which are inundated in the winter and dry out in summer, allowing for a 4-month growing season from August to November.

It usually occurs on the coast, in association with plants such as Salicornia perennans and Suaeda maritima, but is sometimes found inland at heights up to 180 m.[17] Britain is at the northern edge of its natural range, and saltmarsh goosefoot is largely restricted to the grazing marshes of the Thames Estuary, where it grows on the banks of brackish ditches that are poached by cattle, or in shallow rills in the fields, which dry out in the summer.