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

[1] Found in Venezuela, it was formally described as a new species in 2014 by Dutch lichenologist André Aptroot.

P. neuwirthii is similar to Polymeridium quinqueseptatum but can be differentiated by its hamathecium inspersed with large oil droplets and consistently 7-septate, rough ascospores.

The type specimen was collected in Puerto Ayacucho, Venezuela, on a twig of a shrub.

The species is named in honour of the collector of the type and only specimen, Gerhard Neuwirth.