Marsh rat can refer to several not closely related types of semiaquatic rodents of superfamily Muroidea:
Dasymys, about ten species from Africa in the family Muridae; African marsh rat or common dasymys (D. incomtus) Angolan marsh rat (D. nudipes) Holochilus, three species from South America in the family Cricetidae; Amazonian marsh rat, common marsh rat or simply the marsh rat (H. sciureus) Brazilian marsh rat or web-footed marsh rat (H. brasiliensis) Chacoan marsh rat (H. chacarius) Greater marsh rat (Lundomys molitor), a cricetid from southeastern South America; Marsh rice rat (Oryzomys palustris), a cricetid from southeastern North America.