Polymeridium albidoreagens is a species of corticolous (bark-dwelling) lichen in the family Trypetheliaceae.

[1] Found in Brazil, it was formally described as a new species in 2013 by lichenologists André Aptroot, Aline Anjos Menezes, and Marcela Cáceres.

This lichen species is similar to Polymeridium albidum but is characterized by its UV+ (yellow) thallus.

The ecorticate, whitish-grey thallus features spherical, erumpent, solitary ascomata with diameters ranging from 0.2 to 0.4 mm and an apical ostiole.

The hamathecium is not inspersed, and the ascospores number 8 per ascus, contain 3 septa, and measure 20–23 by 6–8 μm without ornamentation.