The Boxer is a breed of stocky, medium-sized, short-haired dog with a smooth fawn or brindled coat and square-jawed muzzle. Boxers are brachycephalic, and have mandibular prognathism (an underbite), very strong jaws and a powerful bite. They are part of the Molosser group of dogs, bred from the extinct German Bullenbeisser and the English Bulldog.