A sled dog is a dog trained and used to pull a land vehicle in harness, most commonly a sled over snow.

Sled dogs have been used in the Arctic for at least 8,000 years and, along with watercraft, were the only transportation in Arctic areas until the introduction of semi-trailer trucks, snowmobiles and airplanes in the 20th century, hauling supplies in areas that were inaccessible by other methods. They were used with varying success in the explorations of both poles, as well as during the Alaskan gold rush. Sled dog teams delivered mail to rural communities in Alaska, Yukon, Northwest Territories and Nunavut. Sled dogs today are still used by some rural communities, especially in areas of Russia, Canada, and Alaska as well as much of Greenland. They are used for recreational purposes and racing events, such as the Iditarod Trail and the Yukon Quest.

Sled dogs are used in countries and regions such as Canada, Greenland, Siberia, Russia, Norway, Sweden, and Alaska.

A 2017 study showed that 9,000 years ago, the domestic dog was present at what is now Zhokhov Island, northeastern Siberia, which at that time was connected to the mainland. The dogs were selectively bred as either sled dogs or hunting dogs, implying that a sled dog standard and a hunting dog standard co-existed. The optimal maximum size for a sled dog is 20–25 kg (44–55 lb) based on thermo-regulation, and the ancient sled dogs were between 16 and 25 kg (35 and 55 lb). The same standard has been found in the remains of sled dogs from this region 2,000 years ago and in the modern Siberian Husky breed standard. Other dogs were more massive at 30 kg (66 lb) and appear to be dogs that had been crossed with wolves and used for polar bear hunting. At death, the heads of the dogs had been carefully separated from their bodies by humans. Anthropologists speculated that this might have been for ceremonial reasons.

The Kungur Chronicle and the Remezov Chronicle, created at the end of the 16th century and 1703 respectively, tells about the people living along Siberian rivers, whose primary means of transport was riding on reindeer or dogs. In these documents, the rivers Olenyok, Yana, Indigirka and Kolyma were called "dog rivers", as they were rich in fish for the dogs to eat. Rivers with no fish or not enough to feed the dogs were called "deer rivers," as reindeer were then used for transportation.

From the 1940s to the 1990s, Russian dog sled numbers were in decline. The breed population reached an all-time low of 3,000 in 1998 before revival efforts took off. Reasons for their decline include

After World War II, skijor and pulka style dog sled racing gained rapidly in popularity in Norway and neighboring Scandinavian countries. These styles of racing required small, fast teams of 1–4 dogs who competed over short, hilly distances of 15–30 km (10–20 mi). Required to use purebred dogs by the Norwegian Sled Dog Racing Association, the German Shorthair Pointer quickly emerged as the dog breed of choice. At the beginning of the 1970s, the "sled pointer" had emerged, a pointing dog who was bred exclusively for sledding and not hunting. During the 1970s, "Nome-style" sled racing, which mimicked the big sled dog teams running long distances and overnighting in subzero temperatures seen in North American-style races, started to attract interest in Scandinavia. In 1974, the first Nome-style sled race, the Skjelbreia Sweepstakes, was hosted near Oslo. For this style of racing, Norwegian mushers began to import Alaskan huskies; popularized by mushers like Stein Havard Fjelstad and Roger Leegaard who traveled to Alaska to race in the Iditarod. However, as a performance crossbreed, the Alaskan husky could not be legally raced in Norway until 1985, when the Norwegian Sled Dog Racing Association removed the requirement that sled dogs be purebred.

This new ruling also paved the way for Nordic-style mushers to breed their best performing dogs regardless of breed, with mushers mixing Alaskan husky and German Shorthair Pointer to produce the Eurohound as well as Greyhound with German Shorthair Pointer to produce the Greyster. These Nordic-style crossbreeds gained in popularity across Europe and later North America, especially with the rise in popularity of dryland mushing, such as bikejoring and canicross.