Taxonomic accounts are given to four species of Jania, Rhodophyta from Korea; J. adhaerens Lamouroux, J. nipponica (Yendo) Yendo, J. radiata (Yendo) Yendo and J. yenoshimensis (Yendo) Yendo. J. adhaerens is an epiphyte and characterized by massive tufts with decussate-dichotomous branches. J. nipponica growing on the rocks is different from other plants by erect tuft with low-angle dichotomous branches. J. radiata has a small epiphytic thallus (5 mm) and flat, flabellate-dichotomous branches. And J. yenoshimensis grows on the rocks in sublittoral regions and has compressed, fastigate, regular-dichotomous branches. This species is distinguished form others by the formation of slender moniliform branchlets. Among these, J. yenoshimensis is first reported in Korea in this study.