This study aims to identify and characterize the fungus associated with leaf spot symptoms on Heracleum moellendorffii (Apiaceae) in Korea. Diseased leaf samples were collected from three locations in Korea, and fungal isolates were obtained and examined. Its morphological characteristics were consistent with those of the genus Septoria. In multilocus phylogenetic analyses using the internal transcribed spacer region, the large subunit rDNA, translation elongation factor 1-alpha, and β-tubulin gene sequences, the isolates formed a distinct lineage within the Septoria dearnessii clade, indicating that they are closely related to S. dearnessii but genetically differentiated. This study provides the first report of a Septoria species associated with leaf spot on H. moellendorffii.