Sled dogs or sledge dogs are highly trained types of dog that are used to pull a sled, a wheel-less vehicle on runners also called a sledge or sleigh, over snow or ice, by means of harnesses and lines.

Dog sled teams are put together with great care and the effort involves picking leader dogs, point dogs, swing dogs and wheel dogs. The lead dog is very treasured, and seldom will mushers let these dogs out of their sight. Important too is to have powerful wheel dogs to pull the sled out from the snow. Point dogs (optional) are located behind the leader dogs, swing dogs between the point and wheel dogs, and team dogs are all other dogs in between the wheel and swing dogs and are selected for their endurance, strength and speed as part of the team.

Dog power has been utilized for hunting and travel for hundreds of years. As far back as the 10th century these dogs were contributing to human survival and achievements.

Dog-sledding has become a popular winter recreation and sport in North America and Europe. Several distinct dog breeds have been specifically bred for the purpose of pulling sleds, and there is also a long history of using other breeds or crossbreeds as sled dogs. There are two main qualities that are expected in sled dogs: endurance and speed. Racing sled dogs travel up to an average 20 mph (32 km/h) over distances up to 25 mi (40 km).

A sled, sledge, or sleigh is a land vehicle with a smooth underside or possessing a separate body supported by two or more smooth, relatively narrow, longitudinal runners that travels by sliding across a surface. Most sleds are used on surfaces with low friction, such as snow or ice. In some cases, sleds may be used on mud, grass, or even smooth stones. They may be used to transport passengers, cargo, or both. Shades of meaning differentiating the three terms often reflect regional variations depending on historical uses and prevailing climate.

In Britain the three terms are generally quite similar in meaning, although sledge usually refers to a smaller sled, used mostly for freight, one that can generally transport no more than one or two persons with only a limited amount of cargo. Sledges may be pulled by dogs or other smaller animals, although confusingly a sledge pulled by a dog in British English is often referred to as a dog-sled. A small recreational sled, pulled by humans, can also be referred to as a sledge.Sleigh (pronounced "slay") remains largely a synonym for sled regardless of its capacity (and similarly in Canada).

The domestic dog (Canis lupus familiaris), is a subspecies of the gray wolf (Canis lupus), a member of the Canidae family of the mammilian order Carnivora. The term "domestic dog" is generally used for both domesticated and feral varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in human history. The word "dog" may also mean the male of a canine species, as opposed to the word "bitch" for the female of the species.

The present lineage of dogs was domesticated from gray wolves about 15,000 years ago. Remains of domesticated dogs have been found in Siberia and Belgium from about 33,000 years ago. None of these early domestication lineages seem to have survived the Last Glacial Maximum. Although mDNA suggest a split between dogs and wolves around 100,000 years ago no specimens predate 33,000 years ago that are clearly morphologically domesticated dog.

Dogs' value to early human hunter-gatherers led to them quickly becoming ubiquitous across world cultures. Dogs perform many roles for people, such as hunting, herding, pulling loads, protection, assisting police and military, companionship, and, more recently, aiding handicapped individuals. This impact on human society has given them the nickname "Man's Best Friend" in the Western world. In some cultures, dogs are also source of meat. In 2001, there were estimated to be 400 million dogs in the world.