Hydrus is a small constellation in the southern sky. Hydrus may also refer to: Hydrus (Chinese astronomy), constellations recognized in China Hydrus (legendary creature), a creature from Medieval bestiaries Hydrus (roller coaster), a Gerstlauer Euro-Fighter roller coaster at Casino Pier Hydrus (software), a software suite for simulating subsurface water flow SS Hydrus, a Great Lakes freighter See also Hydros (disambiguation)