Hadopyrgus is a genus of white or transparent freshwater snails found only in New Zealand. They are micromolluscs, just a few millimetres long, in the gastropod family Tateidae. Hadopyrgus species are subterranean – living in caves, underground aquifers, or deep in river gravels – and so were named from the Greek hades (underworld) and pyrgos (tower). They can have quite restricted ranges: Hadopyrgus ngataana, for example, has been found in just one pool, in a stream flowing through a single cave.