They are descended from the same stock as the Norwegian Spelsau, and were brought to Iceland by the Vikings.
Icelandic sheep have been bred for a thousand years in a very harsh environment. Consequently, they are quite efficient herbivores.
The Icelandic sheep (Icelandic: ķslenska sauškindin) is a breed of domestic sheep. The Icelandic breed is one of the Northern European short-tailed sheep, which exhibit a fluke-shaped, naturally short tail. The Icelandic is a mid-sized breed, generally short legged and stocky, with face and legs free of wool. The fleece of the Icelandic sheep is dual-coated and comes in white as well as a variety of other colors, including a range of browns, grays, and blacks. They exist in both horned and polled strains. Generally left unshorn for the winter, the breed is very cold-hardy. Multiple births are very common in Icelandic ewes, with a lambing percentage of 175% - 220%.