Two marine ulvalean species (Chlorophyta) were collected from the southern and eastern coasts of Korea. One is morphologically characterized by usually unbranched or little branched ribbon-shaped thalli, fronds with spirally twisted basal portions and usually undulate margins and 1 (-2) pyrenoids per cell. The other has irregularly shaped thalli, undulate and dentate margins in the fronds, small macroscopic denticulations along the margin and (1-) 2-3 pyrenoids per cell. In phylogenetic tree based on molecular data, the two species nest in the same clade with Ulva flexuosa and U. rigida, respectively. These two Korean entities are identified as U. flexuosa and U. rigida, respectively, based on morphological and molecular analyses. This is the first record of Ulva flexuosa and U. rigida in Korea.