Monomorium antarcticum is an ant of the family Formicidae, endemic to New Zealand. Likely New Zealand's most common native ant, also known as the southern ant. Highly variable in size (3-5mm), colour and colony structure it is possible that it consists of a complex of closely related species. It is ubiquitous in a wide range of grassland, scrub and urban habitats. Monomorium antarcticum may occasionally enter houses, but does not form trails. It has a generalist diet including small arthropods, nectar, seeds as well as tending aphids, scale insects and mealy-bugs to obtain honeydew.