Lutreolina is a genus of opossum found in South America. Both extant species in this genus are known as lutrine opossums. They have an otter-like body plan and occasionally semiaquatic tendencies, hence the genus name Lutreolina, which is Latin for "otter-like". Formerly, only one species, the big lutrine opossum (previously known as just the lutrine opossum) was recognized, but a 2014 study described a second species, Lutreolina massoia, on genetic and morphological grounds. There are also two fossil species recognized, Lutreolina biforata (formerly placed in Hyperdidelphys) and Lutreolina materdei.