Dasymys is a genus of semiaquatic rodents in the subfamily Murinae, the Old World rats and mice. The genus is endemic to Africa. These rats are wetland habitat specialists, occurring in marshy areas with wet ground and thick vegetation, such as swamps and vleis. They swim well. They are nocturnal and solitary. Species are more common in the northern regions of Sub-Saharan Africa, likely because their wetland habitat is more degraded in southern regions. The genus is not well studied and its taxonomy is not clear. The number of species and their relationships have only been tentatively determined. Species include: