Desmarestiaceae is a family of brown algae, one of two families in the order Desmarestiales. There are three genera in this family. Two are monotypic, Himantothallus (species name Himantothallus grandifolius) and Phaeurus (species name Phaeurus antarcticus). These are both endemic to Antarctica. The third genus, Desmarestia, has 30 to 40 species. The thalli of some Desmarestia contain vacuoles of sulfuric acid with a pH as low as 0.44. These likely evolved to deter predators. These algae have a very sour taste. They can also have a bad odor when they are removed from the water.