Muellerella is a genus of lichenicolous lichens in the family Verrucariaceae. The genus has a widespread distribution, especially in northern temperate areas, and contains species that live on other lichens, or on liverworts.
Molecular phylogenetic analysis published in 2019 indicates that the genus, as currently circumscribed, is polyphyletic. M. atricola and M. lichenicola form one monophyletic lineage in the genus, but the rest of the species tested fell into two distinct monophyletic lineages. The authors suggest the placement of the genus within the subclass Chaetothyriomycetidae, but acknowledge that more genetic analysis is required to determine the correct placement of the type species, Muellerella polyspora.