Fasciola hepatica, also known as the common liver fluke or sheep liver fluke, is a parasitic trematode (fluke or flatworm, a type of helminth) of the class Trematoda, phylum Platyhelminthes that infects the livers of various mammals, including humans. The disease caused by the fluke is called fascioliasis or fasciolosis, which is a type of helminthiasis and has been classified as a neglected tropical disease. F. hepatica is distributed worldwide, has been known as an important parasite of sheep and cattle for hundreds of years and causes great economic losses in sheep and cattle. Because of its size and economic importance, it has been the subject of many scientific investigations and may be the best-known of any trematode species.