The reindeer (Rangifer tarandus), also known as the caribou in North America, is a species of deer native to Arctic and Subarctic regions. This includes both resident and migratory populations. While overall widespread and numerous, some of its subspecies are rare and at least one has already gone extinct.

Reindeer vary considerably in color and size. Both sexes grow antlers, though in a few populations females lack antlers completely. Antlers are typically larger in males.

Wild reindeer hunting and herding of semi-domesticated reindeer (for meat, hides, antlers, milk and transportation) are important to several Arctic and Subarctic peoples. The reindeer is well known in folklore due to Santa Claus's sleigh being pulled by flying reindeer, a popular element of Christmas. In Lapland, reindeer pull pulks.