The swamp antechinus (Antechinus minimus), also known as the little Tasmanian marsupial mouse, is a species of shrew-like marsupial of the family Dasyuridae and as such is related to dunnarts, quolls and the Tasmanian devil.

The species is nocturnal and partly diurnal or active at night and daytime, whether it is crepuscular is not known.

The species breeds during May–July and gives birth in July–August after 28–32 days gestation to 6–8 joeys.

In the inland areas, mating occurs one month earlier, but the reason is not known.

Few females survive a second year and all males do not live long past the mating period (Wilson et al.