Anders Sandøe Ørsted, also written as Anders Sandoe Oersted or Anders Sandö Örsted (21 June 1816 – 3 September 1872) was a Danish botanist, mycologist, zoologist and marine biologist. He was the nephew of physicist Hans Christian Ørsted and of politician Anders Sandøe Ørsted.^[1]

In his early career, he published on Danish and Arctic nematodes^[2][3] and on the zonation of marine algae in Øresund.^[4]

Between 1845 and 1848, he travelled extensively in Central America and the Caribbean and published numerous papers on the flora, concentrating on the plant families Acanthaceae and Fagaceae.^{[5][6][7][8][9]} One of his better known publications is L'Amérique Centrale.^[10]

He was appointed professor of botany at the University of Copenhagen in 1851, a post he held until 1862. He was succeeded by Ferdinand Didrichsen.

His studies of what has since been known as juniper-pear rust showed that this fungus annually switches between two hosts; Juniperus sabina is the primary (telial) host and pear, Pyrus communis, is the secondary (aecial) host. He thus was the first to discover that some plant-parasitic fungi are heteroecious.^[11] These studies were continued on other Gymnosporangium species.^[12]

The orchid genus Oerstedella Reichenbach f. is named for him.

He is the author of several hundred plant names still in use.^[13]