Eucalypt is any woody plant with capsule fruiting bodies belonging to one of seven closely related genera found across Australia: Eucalyptus, Corymbia, Angophora, Stockwellia, Allosyncarpia, Eucalyptopsis and Arillastrum. In Australia, they are commonly known as gum trees.

Eucalyptus is a genus of more than 700 species of flowering plants in the family Myrtaceae. Most species of Eucalyptus are trees, often mallees, and a few are shrubs. Along with several other genera in the tribe Eucalypteae, including Corymbia and Angophora, they are commonly known as eucalypts or "gum trees". Plants in the genus Eucalyptus have bark that is either smooth, fibrous, hard, or stringy, the leaves have oil glands, and the sepals and petals are fused to form a "cap" or operculum over the stamens. The fruit is a woody capsule commonly referred to as a "gumnut".