Sclerotinia is a fungal genus of significant agricultural and scientific importance, as it includes multiple plant pathogens and provides an informative case study for mechanisms of host generalism. However, the taxonomy of this group remains unsettled, which hinders research on these pathogens. The last monographic treatment of Sclerotinia was published more than 40 years ago and was centered on the morphological data available at that time. Here, we examine that revision alongside other pivotal publications to trace the taxonomic history of Sclerotinia and to evaluate the morphological traits used to identify Sclerotinia species. We also briefly assess the composition of genera in the family Sclerotiniaceae, emphasising the need for a modern taxonomic investigation of the broader group. Thirteen new Sclerotinia species have been described since the last taxonomic revision, including Sclerotinia antarctica, S. asari, S. atrostipitata, S. cirsii-spinosissimi, S. ginseng, S. glacialis, S. himalayensis, S. nivalis, S. pseudoplatani, S. subarctica, S. tetraspora, S. trillii, and S. verrucispora. These species are evaluated here. Finally, several recommendations are made regarding how future taxonomic research on Sclerotinia should incorporate molecular data. We highlight potential obstacles and opportunities for this research, including the limitations of the internal transcribed spacer rDNA region (ITS) as a DNA barcode and the untapped potential of genomic data for the genus. By outlining the gaps that need to be addressed, this review charts a course toward a clearer understanding of taxonomic relationships among Sclerotinia species. This understanding will facilitate research into other aspects, such as pathogenicity and host generalism, and may ultimately contribute to improved management of the devastating diseases caused by these pathogens.