Eucalyptus diversicolor, commonly known as karri,[2] is a species of flowering plant in the family Myrtaceae and is endemic to the south-west of Western Australia.

It is a tall tree with smooth light grey to cream-coloured, often mottled bark, lance-shaped adult leaves and barrel-shaped fruit.

[10] The bark on the trunk and branches is smooth, grey to cream-coloured or pale orange, often mottled and is shed in larger plates, short ribbons or small polygonal flakes.

[16] Eucalyptus diversicolor was first formally described in 1863 by the botanist Ferdinand von Mueller in his book Fragmenta Phytographiae Australiae.

[17][18] The type specimen was collected in 1860 by the botanist Augustus Frederick Oldfield near Wilson Inlet, the location given, in Latin, is In Australiae regionibus depressioribus quam Maxime austro occidentalibus, ubi Blue Gum-tree vocatur.

[12] The botanical name diversicolor is taken from the Latin word diversus meaning to turn apart and color or "separate colours" and refers to the difference between the top of the leaf and its underside.

The defining feature of this section is having inflexed stamens, flattened ovoid seed shape, enclosed valves of the fruit and the lack of pith glands in the branchlets.

Although it has no closely related species it has some affinity with tall Eucalypts found the wet forests of eastern Australian including E. saligna and E. grandis all of which have discolorous adult leaves and seeds with a flattened-ovoid shape.

[12] The climate over the range of the tree is mildly temperate with small variations in humidity and temperature with frosts only occurring on rare occasions.

[3] Karri occurs only within the High Rainfall Zone of the South West Botanical Province of Western Australia which receives 900 to 1,300 millimetres (35.4 to 51.2 in) of rain per year, mostly in winter.

[21] It mostly occurs within the Warren biogeographic region, but there are some outlying populations including the Porongorup Ranges, Mount Manypeaks, Torbay, Rocky Gully all along the south coast and Karridale and Forest Grove to the north west[21] and the Leeuwin-Naturaliste Ridge to the south of Margaret River to the west of the main belt.

[23] The species is considered invasive in South Africa where it is a problem in the Western Cape region and is locally known a karie.

It commonly invades clearings, fynbos, water courses and road sides often out competing local species and is spread easily by seed dispersal.

[5] The soil in which the species grows is often poor, and the tree tends to flower after fire to take advantage of the nutrients released by the combustion of forest litter.

The karri supports an extensive ecosystem which is connected to the granite outcrops of the lower south-west and the many subsequent creeks and rivers created from runoff.

Karri generally dominate in the deep valleys between granite outcrops surrounding the creeks and rivers.

A dense understorey is found in karri forest areas which retains moisture over the hot summers.

The production of seed is dependent on a multitude of variables including tree density, availability of pollinators, soil moisture, genetics, nutrients and fire.

The virtues of the wood were promoted in the 1920s by the state conservator of forests, Charles Lane-Poole, who noted the colonists' preference for other timber as its vulnerability to white ants made it a poor choice for fence posts and railway sleepers.

The timber found uses in the state for wagon spokes and wooden pipes, and in England it was found suitable for scantlings by the national railway and telegraph arms by the postal services and was listed among Lloyds shipbuilding timbers as possessing great strength over large lengths.

The heartwood is golden to reddish brown, often with an orange or purple cast, and tends to darken with age.

Some of the main streets of early Sydney were paved with blocks of Karri but have been long since covered by asphalt.