cismontanum, commonly known as tantoon,[2] is a subspecies of flowering plant in the family Myrtaceae and is endemic to near-coastal areas of eastern Australia.

It is a shrub or small tree with elliptical leaves and white flowers in spring.

Flowering occurs in September and October and the fruit is a capsule 5–7 mm (0.20–0.28 in) in diameter.

[2][3] This subspecies was first described in 1989 by Joy Thompson in the journal Telopea, from specimens collected near Dungog in 1975.

cismontanum is common in near-coastal forests between Fraser Island in Queensland and Gosford in New South Wales.