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

The lichen was formally described as a new species in 2016 by lichenologists Adam Flakus and André Aptroot.

The type specimen was collected in the Kaa-Iya del Gran Chaco National Park and Integrated Management Natural Area (Cordillera Province, Santa Cruz) at an elevation of 278 m (912 ft); there it was found in the Chiquitano dry forests.

[2] The thallus of the lichen is grey, smooth to somewhat bullate, and covers an area of up to about 6 cm (2.4 in) in diameter.

The species epithet xanthoexcentricum refers to two main characters of this lichen: the presence of lichexanthone and the eccentric ostiolar placement.