Opisthorchiidae is a family of digenean parasitic flatworms. Opisthorchiidae have cosmopolitan distribution. The most medically important species in the family Opisthorchiidae are Clonorchis sinensis, Opisthorchis viverrini and Opisthorchis felineus, that are causing disease clonorchiasis. Some species are parasites of economically important fish, e.g. Clarias gariepinus.