Wirthiotrema xanthopustulatum is a species of corticolous (bark-dwelling) lichen in the family Graphidaceae.

Found in Brazil, it was formally described as a new species in 2021 by lichenologists André Aptroot and Maria Fernanda de Souza.

The type specimen was collected in Tagaçaba Porto da Linha (Guaraqueçaba, Paraná) on tree bark.

It has a pale olivaceous, shiny metallic-green thallus that covers an area up to 10 cm (4 in) in diameter.

This latter compound causes the lichen thallus to fluoresce a yellow colour when shone with a long-wavelength UV light.