Fucose is a hexose deoxy sugar with the chemical formula C6H12O5. It is found on N-linked glycans on the mammalian, insect and plant cell surface, and is the fundamental sub-unit of the fucoidan polysaccharide. α(1→3) linked core fucose is a suspected carbohydrate antigen for IgE-mediated allergy. Two structural features distinguish fucose from other six-carbon sugars present in mammals: the lack of a hydroxyl group on the carbon at the 6-position (C-6) and the L-configuration. It is equivalent to 6-deoxy-L-galactose.In the fucose-containing glycan structures, fucosylated glycans, fucose can exist as a terminal modification or serve as an attachment point for adding other sugars.

L-Fucose is claimed to have application in cosmetics, pharmaceuticals, and dietary supplements.