thumb|[[Detection dog of the Metropolitan Police patrolling in London]]
thumb|[[Guide dog in Brazil]]
thumb|[[Šarplaninac livestock guarding dogs at work in the Šar Mountains]]
A working dog is a dog used to perform practical tasks, as opposed to pet or companion dogs.
Definitions vary on what a working dog is, they are sometimes described as any dog trained for and employed in meaningful work; other times as any dog whose breed heritage or physical characteristics lend itself to working irrespective of an individual animal's training or employment; and other times again it is used as a synonym for herding dog.
Working dog types
thumb|[[Search and rescue dog working in Seoul]]
Roles performed by dogs that sometimes sees them classified as working dogs include:
- Assistance or service dog, trained to help a disabled person in some way, such as guiding a visually impaired person, providing mobility assistance, and psychiatric service. Often overlap with therapy dog historically used to provide protection to carriage passengers or merchandise
- Detection dog traditionally used to pull small carts. Now survive in modern age as a novelty or in carting sport.
- Guard dog, trained in combat, or used scouts, sentries, messengers, mercy dogs, and trackers
- School dog, different from assistance or service dogs and trained for animal-assisted education
- Search and rescue dog
- Working terrier, a terrier bred to hunt small mammals, such as badgers, foxes, and rats
Kennel club classification
thumb|left|Historically, [[drafting dogs were common. A photochrom from the late 19th century showing two peddlers selling milk from a dogcart near Brussels, Belgium.]]
When competing in conformation shows, a number of kennel clubs classify various pedigree dog breeds into a "working group" or "working dogs group", although it varies between kennel club what breeds are so classified. The Kennel Club classifies mastiff, pinscher, sled dog, select livestock guardian dog and some other breeds in their working group. The American Kennel Club's working group and the Canadian Kennel Club's working dogs group are very similar to The Kennel Club's except they include all livestock guardian dog breeds and all full sized spitz breeds (not just sled dogs) recognised by the clubs. Both the Australian National Kennel Council's and New Zealand Kennel Club's working dogs groups comprise herding dog breeds and select livestock guardian dog breeds recognised by those clubs. The Fédération Cynologique Internationale has no working group.