Gwenneth Jean Harden OAM (born 1940) is an Australian botanist and author. In 1990 the first of her four volumes of the Flora of New South Wales was published. The four-volume set was fully revised in 2000. The nightcap oak (Eidothea hardeniana) is named in her honour. The standard author abbreviation G.J.Harden is used to indicate this person as the author when citing a botanical name.