Coccocarpia melloniorum is a rare species of foliicolous (leaf-dwelling) lichen in the family Coccocarpiaceae.

The species name melloniorum honours the contributions of the Andrew W. Mellon Foundation for their support to museums, art conservation, and the Global Plants Initiative project, "an international partnership of herbaria working to create a coordinated database of information and images of plant type specimens worldwide ... including fungi and lichens".

[2] The thallus of Coccocarpia melloniorum is epiphyllous (growing on leaves) and microfoliose, with a rounded to irregular outline and diameter ranging from 5–15 mm.

The lower surface is pale to dark brown, with numerous black, branched rhizines measuring 0.3–0.5 mm long.

[2] Coccocarpia melloniorum is distinguished from similar species by its numerous squamiform isidia, which are mostly laminal, rounded, and sometimes irregular or elongate.