Buellia is a genus of 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 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 about 450 species. Genetic studies indicates that the genus Amandinea and Buellia may be the same, although this is not widely accepted.