The southern giant salamander (Isthmura maxima, in Spanish salamandra gigante de Putla) is a species of salamander in the family Plethodontidae. It is endemic to Mexico and known from western and southern Oaxaca. It is the largest tropical salamander. This little-known salamander has been found in a banana field and a roadside bank. It appears to live in permanent burrows. Although it seems to tolerate some habitat modification, urbanization and changed agricultural practices are potential threats.