Five new fungal taxa found on Alnus, a valuable timber tree widely distributed in Europe, are described using morphology and multigene phylogenetic analyses. The new Dothideomycetes, Helminthosporium italicum, Dothiorella guttulata, and Prosthemium alni, and Sordariomycetes, Ditopella aseptatospora and Cryptosporella alni-cordatae, are compared with similar taxa and the differences are discussed.