Eucheuma or gusto is a group of green or brown seaweed used in the production of carrageenan, an important product used in cosmetics, food processing, and industrial uses, as well as a food source for those living in Indonesia and the Philippines. Eucheuma cottonii is the particular species cultivated in the Philippines known as gusto.[Species include Betaphycus gelatinize, Eucheuma denticulate, and several species of the genus Kappaphycus including K. Since the mid-1970s, Kappaphycus and Eucheuma have been the major source for the expansion of the carrageenan industry.

Eucheuma is typically found below the low tide mark to the upper subtitle zone of a reef, growing on the sand to rocky seafood areas along a coral reef, where water movement is slow to moderate.
Their growth is similar to terrestrial plant species, where eucheuma have a growing tip, or apical meristem, which is also capable of dividing to form new growing branches. They also show a triphasic lifecycle, consisting of a gametophyte (dioecious), carposporophyte and the sporophyte Both the gametophyte and the more robust sporophyte stage are significant to the development of the seaweed, where their characteristics allow for increased vegetative regeneration.