Blastodesmia is a monotypic fungal genus in the family Pyrenulaceae.

[2] It contains the single species Blastodesmia nitida,[3] a corticolous (bark-dwelling) crustose lichen found in Europe.

Both the genus and the species were described in 1852 by the Italian botanist Abramo Bartolommeo Massalongo.

[4] Historically, two other species have been included in the genus, but are currently not accepted by Species Fungorum:[3] Characteristics of genus Blastodesmia include paraphyses in the hamathecium, transversely septate ascospores that are grey to brown in colour, and pyrenocarp-type ascomata with carbonized ascoma walls.

The ascospores are mostly 37–47 μm long and have a constriction at the septa.