Dollar spot is one of the most economically important fungal diseases of warm- and cool-season turfgrass species. Over the past several decades, the 'true' identity of the fungus causing the disease has been the subject of much debate. Morphological and rDNA sequence data have suggested the fungus is a member of the Rutstroemiaceae family rather than the Sclerotiniaceae, however, these data are inadequate to determine placement within the group. In this study, 58 cultured isolates and 258 herbarium specimens from the U.S. National Fungus Collections were evaluated using multilocus molecular phylogenetic analysis to determine the “true” identity of the causal agent of dollar spot disease in turfgrass. The sample included members of the Rutstroemiaceae and Sclerotiniaceae (e.g. Ciboria, Lanzia, Monilinia, Poculum and Rustroemia) and exemplar strains of the dollar spot fungus. Authenticated herbarium samples ranged from 25 to 132 years old, and included type specimens of Ciboria, Lambertella, Lanzia, Rutstroemia, Sclerotinia species and the original materials used by Bennett to describe the dollar spot fungus in 1937. ~4300-bp of DNA sequence data from eight genes were generated from cultured isolates (rDNA internal transcribed spacer region [ITS], calmodulin [CAL], translation elongation factor 1 alpha, DNA replication factor Mcm7, actin, beta tubulin, and the large [LSU] and small subunits of the rDNA). From the herbarium specimens, PCR was optimized to amplify short fragments from the degraded “ancient” DNA (<400bp) from the ITS, CAL and LSU regions to connect the molecular data from modern samples to validly described taxonomic groups. In conjunction with morphological assessments, these data are currently being used to precisely characterize phylogenetic affiliations between the dollar spot fungus and closely related fungi, to distinguish species and genus-level boundaries, and to develop the formal taxonomic and nomenclatural diagnosis required to provide a legitimate name for the dollar spot fungus.