The Old Norwegian Spælsau, as the name suggests, is a Norwegian sheep breed rooted in the Old Norwegian sheep—the most original type of sheep in Norway. This breed was officially defined as a separate breed in 2002 and has since been recognized for its unique traits and historical significance.  

The breed likely dominated in Norway until the 1600s–1700s. In the early 1700s, sheep were imported from Britain that were larger, had finer wool, long tails, and higher slaughter weights. As agriculture became more intensive, these imported sheep were preferred over the local short-tailed breeds. This development almost led to the disappearance of the original Norwegian sheep breeds.  

Today (2023), there are around 14,000 Old Norwegian Spælsau individuals, meaning the breed is not classified as endangered. However, it remains vulnerable, making it essential to monitor the population to prevent it from becoming threatened. Current breeding efforts focus on preserving the diversity of the sheep's color variations, which include black, gray, blue, brown, light brown, white, and white markings on the head and body. Rare and historical color patterns such as grelet, mouflon coloring, and English gray are also prioritized for preservation.