The stoat (Mustela erminea), also known as the short-tailed weasel, is a mammal of the genus Mustela of the family Mustelidae native to Eurasia and North America, distinguished from the least weasel by its larger size and longer tail with a prominent black tip. Originally from Eurasia, it crossed into North America some 500,000 years ago, where it naturalized and joined the notably larger, closely related native long-tailed weasel.