A new distribution of Scutellaria guilielmii A. Gray is discovered in Korea. This species was collected from seashores on Pyoseon-ri, Pyoseon-myeon, Seogwipo-si, Jeju-do. S. guilielmii is distinguished from other related Korean taxa of the genus by having broadly winged nutlets (fruits). Here, we provide a precise description, illustrations, key to the related taxa, and photographs of its habitat. The new Korean name is given as ‘Nal-gae-gol-mu-kkot’, considering the broadly winged nutlets (fruits). In addition, new habitats are likely to be discovered through plant biodiversity surveys of the southwestern coastal islands.