Phacopsis lethariellae is a species of lichenicolous (lichen-dwelling) fungus in the family Parmeliaceae.

It was formally described as a new species in 1995 by Josef Hafellner and Gerhard Rambold.

The type specimen was collected by the first author from La Fortaleza (La Gomera) at an altitude of 1,180 m (3,870 ft), where it was found growing on the thallus of the lichen Lethariella intricata.

It has dark brown to black apothecia that are typically 0.3–0.5 mm in diameter, with a convex disc.

The fungus, known to occur only in the Canary Islands, is named after the genus of its host.