The Jack Russell Terrier is a small, principally white-bodied, smooth or rough-coated terrier. They were first bred by an English clergyman in the 19th century, as working terriers to flush foxes out of their dens so that the foxes could be hunted.

Their high energy and drive make these dogs ideally suited to a number of different dog sports such as flyball or agility. Obedience classes are also recommended to potential owners as Jack Russells can be stubborn at times and aggressive towards other animals and humans if not properly socialized (a process that should be continued throughout their whole lives). Jack Russell Terriers can be very hyperactive. Despite their small size, these dogs are not recommended for the condominium or apartment dweller unless the owner is ready to take on the daunting task of providing the dog with the necessary amount of exercise and stimulation. These are truly big dogs in a small packages, which can sometimes lead to trouble involving larger animals. The JRT owner must be aware of these tendencies and keep an eye out for trouble in many situations.