The stoat (Mustela erminea), also known as the Eurasian ermine, Beringian ermine and ermine, is a mustelid native to Eurasia and the northern portions of North America. Because of its wide circumpolar distribution, it is listed as Least Concern on the IUCN Red List. It is distinct from the long-tailed weasel (Neogale frenata), also known as the "masked ermine", or "big stoat"; the two species are visually similar, especially the black tail tip.

The name ermine () is used for species in the genus Mustela, especially the stoat, in its pure white winter coat, or the fur thereof.Introduced into New Zealand in the late 19th century to control rabbits, the stoat has had a devastating effect on native bird populations. It was nominated as one of the world's top 100 "worst invaders". Ermine fur was used in the 15th century by Catholic monarchs, who sometimes used it as the mozzetta cape. It has long been used on the ceremonial robes of members of the United Kingdom House of Lords. It was also used in capes on images such as the Infant Jesus of Prague.