Hydromedusa is a turtle genus in the family Chelidae, commonly known as the South American snake-necked turtles. They are quite closely related to the South American side-necked swamp turtles (Acanthochelys) and the snake-necked turtles of the Australian-Melanesian region (Chelodina), but less closely to the side-necked river turtles of South America (Podocnemididae) which belong to a more modern lineage of Pleurodira. This genus contains the following species: * Brazilian snake-necked turtle, Hydromedusa maximiliani * Argentine snake-necked turtle, Hydromedusa tectifera