Abstract
A nolid species, Roeselia triangulalis (Leech) is reported for the first time from Korea. Two males were collected from Jeju Island, South Korea. Roeselia triangulalis can be distinguished by the bipectinate male antennae, broad frons, long labial palpi, costally dark brownish spot and the rounded dark brownish postmedial line of forewing. In the male genitalia, the long saccus, the slender valve with distally expanded and spine-like harpe and long spinular cornutus of vesica are distinguishing characters. In the female genitalia, the simple sterigma, the long ductus bursae and the large ovate corpus bursae with a lip-shaped signum are distinguishing characters. Diagnosis and description of the species are given with the figures of the male genitalia.