Which breed of dog is this?

The Airedale Terrier, also called Bingley Terrier and Waterside Terrier, is a dog breed of the terrier type that originated in the valley of the River Aire, in Yorkshire, England.

It is traditionally called the "King of Terriers" because it is the largest of the terrier breeds. The Airedale was bred from the Old English Black and Tan Terrier (now known as the Welsh Terrier), the Otterhound and probably some other Terrier breeds, and has contributed to other dog breeds, such as the Yorkshire Terrier.

Originally bred to serve as a versatile hunting and all around working farm dog, in Britain this breed has also been used as a war dog, guide dog and police dog. In the United States, this breed has been used to hunt big game, upland birds, and water fowl, and serve in many other working capacities.

The Airedale is the largest of the British terriers. They weigh 19–25 kilograms (42–55 lb) in fit condition and have a height at the withers of 58–61 centimetres (23–24 in) for males, with females slightly smaller.

The American Kennel Club standard specifies a very slightly smaller dog. Larger Airedales, up to 55 kilograms (121 lb) can sometimes be found in North America.

The Airedale has a medium-length black and tan coat with a harsh topcoat and a soft undercoat. They are an alert and energetic breed, "not aggressive but fearless."