Prostanthera walteri, commonly known as blotchy mint-bush,[2] is a species of flowering plant that is endemic to south-eastern Australia.

It is a sprawling shrub with tangled, hairy branches, egg-shaped leaves and usually bluish green flowers with prominent purple veins arranged singly in leaf axils.

The lower surface of the leaves is hairy and the upper is grooved and more or less glabrous.

[2][3][4][5] Prostanthera walteri was first formally described in 1870 by Victorian Government Botanist Ferdinand von Mueller in the seventh volume of Fragmenta Phytographiae Australiae, based on plant material collected by Carl Walter at Mount Ellery in East Gippsland.

The specific epithet (walteri) honours the collector of the type specimens.