It has rough bark near the base, smooth white to cream-coloured bark above, lance-shaped to curved adult leaves, flower buds in groups of seven, white flowers and cup-shaped, conical or hemispherical fruit.Eucalyptus dunnii is a tree that typically grows to a height of 50 m (160 ft) and forms a lignotuber.

The flower buds are arranged in groups of seven in leaf axils on a flattened, unbranched peduncle 7–16 mm (0.28–0.63 in) long, the individual buds on a pedicel 2–6 mm (0.079–0.236 in) long.

[2][3][4] Eucalyptus dunnii was first described in 1905 by Joseph Maiden in Proceedings of the Linnean Society of New South Wales from a specimen collected by William Dunn at "Acacia Creek, Macpherson Range".

[5][6][7] The specific epithet (dunnii) honours the collector of the type specimen.

[2][7] Dunn's white gum has a scattered and restricted distribution in wet forest north from Dorrigo and Coffs Harbour in New South Wales to Warwick and Canungra in Queensland.