The Australian Cattle Dog (ACD or Cattle Dog), is a breed of herding dog originally developed in Australia for droving cattle over long distances across rough terrain. The dog was developed in the 19th century, in New South Wales Australia by cattle farmer Thomas Hall, who crossed the dogs used by drovers with dingoes he had tamed. The resulting dogs were known as Halls Heelers and were subsequently developed into two modern breeds, one of them the Australian Cattle Dog. 

The Australian Cattle Dog is a medium-sized, short-coated dog that occurs in two main colour forms. It has either brown or black hair distributed fairly evenly through a white coat, which gives the appearance of a "red" or "blue" dog. It has been nicknamed a "Red Heeler" or "Blue Heeler" on the basis of this colouring and its practice of moving reluctant cattle by nipping at their heels.

As with dogs from other working breeds, the Australian Cattle Dog has a high level of energy, a quick intelligence, and an independent streak. It responds well to structured training, particularly if it is interesting and challenging. Although not aggressive it was bred to bite, and owing to the strong attachment it forms to its owners can be protective of them and their possessions. It is easy to groom and maintain, requiring little more than brushing during the shedding period. Australian Cattle Dogs are a robust breed with a lifespan of 12 to 14 years.