Fucoidans are sulfated, fucose-rich polysaccharides found in brown macroalgae and echinoderms. There is a growing interest in this group of compounds for therapeutic purposes (Fitton, Stringer, and Karpiniec 2015). In this chapter we discuss the classical methods for extraction and characterization of fucoidans from macroalgae, and briefly explore their current applications. The sources of macroalgal biomass used for the extraction of various fucoidans and their key differences and applications are outlined. The methods of extraction of fucoidans are discussed, from classical laboratory techniques to larger-scale commercial processes. The advent of appropriate characterization techniques and the implications of structural variations that these techniques have yielded are emphasized. Fucoidans have been assessed for utility in a broad range of human and animal health-related applications, which are discussed with particular reference to safety and practicality.