A herding dog, also known as a stock dog or working dog, is a type of dog that either has been trained in herding livestock or belongs to one of the breeds that were developed for herding. A dog specifically trained to herd sheep is known as a sheep dog or shepherd dog.

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.