Hydromys is a genus of semiaquatic rodents in the subfamily Murinae. Three species are endemic to New Guinea and nearby islands. The fourth species, the rakali, is also found on Australia. The most recently discovered member of this genus was described in 2005.

List of species

Genus Hydromys - water rats: Note: Hydromys habbema Tate and Archbold, 1941 and Hydromys shawmayeri (Hinton, 1943) are placed within Baiyankamys after Helgen, 2005.