Lecanactis rubra is a species of corticolous (bark-dwelling), crustose lichen in the family Roccellaceae.

The type specimen was collected by Sérusiaux from the gorge of Manambolo (Mahajanga Province) at an altitude of 300 m (980 ft).

At this location, about 3 km (1.9 mi) upstream from Bekopaka, in a dry forest with calcareous soil, it was found growing on bark.

[1] Lecanactis rubra has a cream-coloured, verrucose (pimply), mat thallus that lacks a cortex.

It also has an unidentified anthraquinone that is present as numerous red crystals in the excipulum (the ring-shaped layer surrounding the spore-bearing hymenium); the specific epithet rubra refers to this characteristic.