Caloplaca ahtii is a species of corticolous (bark-dwelling) crustose lichen in the family Teloschistaceae. It was formally described as a new species in 1994 by Ulrik Søchting. The type locality was in Finland, and the type specimen was found growing on Populus. The species epithet honours Finnish lichenologist Teuvo Ahti. In 2022, the species was documented from North-Western European Russia. It is also found in North America.

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