Buellia is a genus of mostly lichen-forming fungi in the family Caliciaceae. The fungi are usually part of a crustose lichen. In this case, the lichen species is given the same name as the fungus. But members may also grow as parasites on lichens (lichenicolous). The algae in the lichen (the photobiont partner) is always a member of the genus Trebouxia.

Lichens in the genus are commonly called disc lichens, or button lichens. The genus has a widespread distribution and contains almost 1000 species.

Genetic studies indicate that the genus Amandinea and Buellia may be the same, although this is not widely accepted.

The genus Buellia was described by Italian botanist Gioseppe De Notaris in 1846 and named after his friend, Esperanzo Buelli.

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