A rust disease occurred on Lysimachia clethroides in Deogyusan National Park, Jeollabukdo. The typical symptoms of the disease appeared as small, yellowish spots on leaves at first. The spots then turned yellowish brown and powdery mass of blackish brown spores appeared on the lesions. Severely infected leaves blighted and eventually shriveled. Teliospores were yellowish brown in color, clavate or fusiform in shape and $38{sim}62;{ imes};14{sim}22;{mu}m$ in size, the apex rounded or obtuse, the base attenuated. Pedicels hyaline, persistence, up to $75{mu}m$ long. The causal fungus was identified as Puccinia dieteliana based on mycological characteristics and host specificity.