Corymbia calophylla, commonly known as marri, is a species of flowering plant in the family Myrtaceae and is endemic to the southwest of Western Australia.

Adult leaves are arranged alternately, thick and glossy green on both sides, broadly lance-shaped to egg-shaped and tapered or rounded at the base.

[5] The name Eucalyptus calophylla was first published in 1831 by Robert Brown in Journal of the Royal Geographical Society of London, but without a description it was deemed to be a nomen nudum.

[14][15][5] In 2009, Carlos Parra-O and colleagues published a combined analysis of nuclear rDNA (ETS + ITS) and morphological characters to clarify relationships within the genus Corymbia.

Other species of Corymbia (then Eucalyptus) were referred to as 'red gum', so to avoid ambiguity the Forestry Department of the Western Australian government nominated the extant name marri in the 1920s.

[2] Marri is regarded as one of the six forest giants found in Western Australia; the other trees include; Eucalyptus gomphocephala (tuart), E. diversicolor (karri), E. jacksonii (red tingle), E. marginata (jarrah) and E. patens (yarri).

The fruit and seeds are consumed by avian species, and it is a staple in the diet of long-billed black cockatoo (Zanda baudinii) and red-capped parrot (Purpureicephalus spurius).

[28][29] Plant species associated with Corymbia calophylla in the mid-story include the tall shrub or tree Persoonia longifolia (snottygobble) and Kingia australis (bullanock) in jarrah-marri woodland, where it dominates the canopy with Eucalyptus marginata.

[31] Eucalypts occurring in its range can be displaced; for example, in metropolitan Perth it overwhelms E. lane-poolei (salmon white gum) on all but wetter Guildford soils.

[33] The species is named as one of the dominant taxa in Corymbia calophylla–Xanthorrhoea preissii woodlands and shrublands of the Swan Coastal Plain, a critically endangered ecological community, once widespread and now restricted to less than 3% of its range.

[34] Old large trees became rare after extensive agricultural conversion of land during the twentieth century, but Mueller recorded specimens in the 1870s with trunks up to three metres in width.

[35] Marri trees played a significant role in Noongar culture, the applications of its products were adapted and exported by the people occupying the Southwest of Australia.

[20][10] The use as a remedy for diarrhoea by people of the region was noted by colonist Jane Dodds of Guildford, Western Australia, "as we do rhubarb but it does not answer for Europeans".

Rosendo Salvado, the Spanish Bishop, contradicts this notion in reporting the efficacy of this remedy for a widespread problem in the new colony, taken in tea or as one or two small lozenges; he says the effect is produced in a day, but also warns that overdose can lead to paralysis.

Early mentions in literature often remark on the blood-like appearance of the kino that flowed from the marri trees in their new environment — the Diary of George Fletcher Moore recording its use in 1831.

The wood's strength was utilised in the nineteenth century for handles, spokes and other implements, and applications in building construction, but found to deteriorate when used below ground.

[5] The blossoms from the marri can be used as a source of sugary syrup, which can be sucked directly from the flower or can be dipped into water to make a sweet drink.

[17][37] The large and distinctive fruit produced by the tree is featured in the literature of May Gibbs, whose childhood in Western Australia arguably influenced her series on 'Gumnut babies'.

[5] Mueller noted in Eucalyptographia (1879) that the tree could be grown in tropical climes, giving John Kirk's report of its successful introduction to Zanzibar, but that its sensitivity to frost had accounted for its failure in Melbourne, Australia and other regions.