The western chestnut mouse (Pseudomys nanus) is a species of rodent in the family Muridae.

[1][2] P. nanus inhabits grasslands and open stands of eucalypt on sandy soil.

Fully grown adult mice weigh around 70 g and have an average body length of 10 cm.

[4] Studies in 1999 showed that the species has an excellent capacity for repleting glycogen following exertion, even if they do not eat.

[5] Populations of western chestnut mouse in the Northern Territory have declined substantially since European colonisation of Australia, with one study identifying a 24% reduction in the extent of occurrence and a 25% reduction in the breadth of occupied environmental space.