Monogeneans, members of the class Monogenea ( ), are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they have both male and female reproductive structures.

Some monogeneans are oviparous (egg-laying) and some are viviparous (live-bearing). Oviparous