In October 2015, a bacterial leaf blight was observed on Miscanthus × giganteus in Jinju, South Korea. Symptoms included chlorosis and necrotic lesions on the leaves. Bacteria belonging to the γ-proteobacteria genus Pseudomonas were isolated from the affected leaves. Physiological analysis, the Biolog system, MALDI-TOF MS, and molecular techniques identified the bacteria isolated as Pseudomonas syringae pv. syringae. Healthy M. × giganteus leaves inoculated with the strain MHGNU B101, isolated from leaf lesions, developed leaf blight. Bacteria re-isolated from the leaf lesions had identical cultural characteristics and rpoD gene sequence to the original strain. This is the first report of P. s. pv. syringae causing bacterial leaf blight on M. × giganteus.