The eastern great egret is a species of heron from the genus Ardea, usually considered a subspecies of the great egret. In New Zealand it is known as the white heron or by its Māori name kōtuku. It was first described by British ornithologist John Edward Gray in 1831.

Herons are long-legged, long-necked, freshwater and coastal birds in the family Ardeidae, with 72 recognised species, some of which are referred to as egrets or bitterns rather than herons. Members of the genera Botaurus and Ixobrychus are referred to as bitterns, and, together with the zigzag heron, or zigzag bittern, in the monotypic genus Zebrilus, form a monophyletic group within the Ardeidae. Egrets do not form a biologically distinct group from herons, and tend to be named differently because they are mainly white or have decorative plumes in breeding plumage. Herons, by evolutionary adaptation, have long beaks.