Martensia jejuensis is a species of red algae.Guiry, M.D. & Guiry, G.M. 2012. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 31 October 2012 This red alga was first described by Lee Yongpil (이용필) in 2004.

In South Korea, it is found in the warm waters of the southern coasts off Mokdo, Bijindo, Chujado, and Jejuhttps://species.nibr.go.kr/home/mainHome.do?cont_link=009&subMenu=009002&contCd=009002&pageMode=view&ktsn=120000000863 (whence it derives its epithet, jejuensis). It is also found off southern Japan, Indonesia, and Australia.

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