Gelidium amansii, also known as by its Korean name umutgasari,[1] is an economically important species of red algae commonly found and harvested in the shallow coast (3 to 10 m or 10 to 33 ft of depth below the water) of many East Asian countries including North and South Korea, China, Japan, Singapore, and northeast Taiwan.

[2] G. amansii can be purple, red, to yellowish-red because it contains the class of pigments known as phycobiliprotein.

G. amansii may have four or five opposite, compound-lobed, pinnate leaves on each branch.

G. amansii is an important food source in East Asian countries and has been shown to have medicinal effects on dieting.

This algae is used to make agar, whose components are the polysaccharide agarose and agaropectin, from the large amount of algin which is located in the algae's cell wall, as well it is sometimes served as part of a salad, puddings, jams, and other culinary dishes in producing regions.