About 40 collections of Pseudobaeospora species from all over Europe have been studied. A key is presented to the 13 species recognised and two provisionally defined ones. Latin diagnoses of six new species, one new variety and one new forma are given. Part one of this paper contains an introduction, a key to the taxa studied and Latin diagnoses of the new taxa. Part two will contain the description of the genus, full descriptions and figures of all taxa treated, and discussions.