Herpothallon nigroisidiatum is a little-known species of corticolous (bark-dwelling), crustose lichen in the family Arthoniaceae.

[1] Found in Peru, it was formally described as new to science in 2009 by the lichenologist Göran Thor.

It is only known to occur at its type locality, which is a tropical rainforest in the Cordillera Escalera [pt], San Martín.

The species epithet nigroisidiatum refers to its pseudisidia, which have a black hypothallus that sometimes projects up into their inner parts and colours them black.

This Arthoniomycetes-related article is a stub.