Pertusaria loeiensis is a rare species of crustose lichen in the family Pertusariaceae.

[1] Found in Thailand,[2] it was formally described as a new species in 2005 by Sureeporn Jariangprasert.

The type specimen was collected from Nahaeo National Park (now known as Phu Suan Sai) (Loei province) at an altitude of 540 m (1,770 ft), where it was found in a dry evergreen forest growing on the bark of Neolithea.

The species epithet combines the province of the type locality with the Latin -ensis ("place of origin").

The main distinguishing characteristics of Pertusaria loeiensis are its asci, which contain only two spores, and the presence of the lichen products 2-O-methylperlatolic acid and stictic acid.