The genus Eucalyptus is host to numerous species of Mycosphaerella, several of which are only known as anamorphs, and for which no Mycosphaerella state is known. In this study new Mycosphaerella teleomorph states are described for Nothostrasseria dendritica and Trimmatostroma excentrica. Two new hyphomycete genera are introduced. Of these, Cibiessia gen. nov., with three new species accommodates an arthoconidial synanamorph of Readeriella. Phaeothecoidea gen. nov. is described for species with brown, thick-walled endoconidia. Four additional new species of Mycosphaerella are introduced with several new anamorph species described in Dissoconium, Phaeophleospora, Pseudocercospora, Ramularia and Stenella, Furthermore, an epitype is designated for Mycosphaerella molleriana. This study also presents new Eucalyptus host and distribution records including M. mexicana from Hawaii, M. ohnowa from Australia, M. acaciigena from Australia and Venezuela, M. heimii from Venezuela and Thailand, M. konae from Venezuela, and M. thailandica from Thailand.