Scent hounds are a type of hound that primarily hunts by scent rather than sight. These breeds are hunting dogs and are generally regarded as having some of the most sensitive noses among dogs. Scent hounds specialize in following scent or smells. Most of them tend to have long, drooping ears and large nasal cavities to enhance smell sensitivity. They need to have relatively high endurance to be able to keep track of scent over long distances and rough terrain. It is believed that they were first bred by the Celts by crossbreeding mastiff-type dogs with sighthounds. The first established scent hounds were St. Hubert Hounds bred by monks in Belgium during the Middle Ages.

Dog types are broad categories of domestic dogs based on form, function, or style of work, lineage, or appearance. Some may be locally adapted dog types that may have the visual characteristics of a modern purebred dog. In contrast, modern dog breeds strictly adhere to long-established breed standards,[note 1] that began with documented foundation breeding stock sharing a common set of inheritable characteristics, developed by long-established, reputable kennel clubs that recognize the dog as a purebred.