Eucalyptus rhombica is a tree that typically grows to a height of 20 m (66 ft) and forms a lignotuber.

The fruit is a woody, cup-shaped or conical capsule 7–10 mm (0.28–0.39 in) long and wide with the valves near rim level.

[2][3] Eucalyptus rhombica was first formally described in 1994 by Anthony Bean and Ian Brooker in the journal Austrobaileya from material collected in the Hungry Hills State Forest near Ceratodus.

[3][4] The specific epithet (rhombica) is from the Latin rhombicus, referring to the shape of the flower buds.

[3] This eucalypt is restricted to three areas near Toowoomba, Gayndah and Taroom, where it grows in sandy soil.