Fucoidan is a long chain sulfated polysaccharide found in various species of brown algae. Commercially available fucoidan is commonly extracted from the seaweed species Fucus vesiculosus, Cladosiphon okamuranus, Laminaria japonica and Undaria pinnatifida. Variant forms of fucoidan have also been found in animal species, including the sea cucumber. Fucoidan occurs in the cell walls of the seaweed plant and serves to protect it from external stresses. The same protective benefits that are of value to the seaweed plant have also found to be of potential benefit for both human and animal health. Fucoidan extracts are utilised in a range of therapeutic health care preparations, being incorporated as high value ingredients in nutritional, medical device, skincare and dermatological products. The bioactivity of fucoidan extracts is largely determined by the fucoidan extraction method and the seaweed species from which it is extracted. Fucoidan extraction methods, purity, bioactivity, global regulatory approvals and source seaweed species vary between fucoidan producers. History Fucoidan-containing seaweeds have a rich history of medicinal and therapeutic use. The earliest records have been unearthed at Monte Verde in Chile, where archaeological digs have uncovered evidence of their use dating to circa 12000 BC. Early therapeutic use was also evident in ancient Greek and Roman civilizations. In the 17th century, the English botanist John Gerard noted the use of seaweed to treat a wide variety of ailments. Fucoidan itself was not isolated and described until the early 1900s. In 1913, Swedish Professor Harald Kylin became the first to describe the slimy film found on many seaweeds as ‘fucoidin’ or ‘fucoijin’. The substance subsequently became known as ‘fucoidan’ based on the international naming convention on sugars. Research in the early 20th century focused on extracting crude extracts and reconciling some of the conflicting views on fucoidan. Methods of extracts and isolation of fucoidan from brown seaweeds were determined on laboratory scale by Black et al. at the Institute of Seaweed Research in the UK. Global research opportunities expanded once fucoidan became commercially available in the 1970s from Sigma Inc. Anti-cancer effects were amongst the first to be reported by Japanese researchers, followed by effects on immune modulation and then anti-tumour, anti-viral and anti-inflammatory responses. Today, fucoidan continues to be used as a complementary therapy in many parts of Asia, namely Japan and Korea, where it is not uncommon for it to be recommended to patients undergoing treatment for cancer. Interest in, and