The stoat, also known as the Eurasian ermine, Beringian ermine and ermine, is a mustelid native to Eurasia and the northern regions of North America. Because of its wide circumpolar distribution, it is listed as Least Concern on the IUCN Red List. It was introduced into New Zealand in the late 19th century to control rabbits, but had a devastating effect on native bird populations and was nominated as one of the world's top 100 "worst invaders".

The Mustelidae are a diverse family of carnivorous mammals, including weasels, stoats, badgers, otters, martens, grisons, and wolverines. Otherwise known as mustelids, they form the largest family in the suborder Caniformia of the order Carnivora with about 66 to 70 species in nine subfamilies.