Fungal communities play a crucial role in maintaining the health of managed and natural soil environments, which directly or indirectly affect the properties of plants and other soil inhabitants. As part of a Citizen Science Project initiated by the Westerdijk Fungal Biodiversity Institute and the Utrecht University Museum, which aimed to describe novel fungal species from Dutch garden soil, the diversity of Didymellaceae, which is one of the largest families in the Dothideomycetes was investigated. A preliminary analysis of the ITS and LSU sequences from the obtained isolates allowed the identification of 148 strains belonging to the family. Based on a multi-locus phylogeny of a combined ITS, LSU, rpb2 and tub2 alignment, and morphological characteristics, 20 different species were identified in nine genera, namely Ascochyta, Calophoma, Didymella, Juxtiphoma, Nothophoma, Paraboeremia, Phomatodes, Stagonosporopsis, and Xenodidymella. Several isolates confirmed to be ubiquitous plant pathogens or endophytes were for the first time identified from soil, such as Ascochyta syringae, Calophoma clematidis-rectae, and Paraboeremia litseae. Furthermore, one new genus and 12 novel species were described from soil: Ascochyta benningiorumsp. nov., Didymella degraaffiaesp. nov., D. kooimaniorumsp. nov., Juxtiphoma kolkmaniorumsp. nov., Nothophoma brennandiaesp. nov., Paraboeremia rekkerisp. nov., P. truiniorumsp. nov., Stagonosporopsis stuijvenbergiisp. nov., S. weymaniaesp. nov., Vandijckomycella joseaegen. nov. et sp. nov., V. snoekiaesp. nov., and Xenodidymella weymaniaesp. nov. From the results of this study, soil was revealed to be a rich substrate for members of Didymellaceae, several of which were previously known only from diseased or apparently healthy plant hosts.