The Australian Cattle Dog, or simply Cattle Dog, is a breed of herding dog developed in Australia for droving cattle over long distances across rough terrain. This breed is a medium-sized, short-coated dog that occurs in two main colour forms. It has either red or black hair distributed fairly evenly through a white coat, which gives the appearance of a "red" or "blue" dog.

As with dogs from other working breeds, the Australian Cattle Dog is energetic and intelligent with an independent streak. It responds well to structured training, particularly if it is interesting and challenging. It was originally bred to herd by biting, and is known to nip running children. It forms a strong attachment to its owners, and can be protective of them and their possessions. It is easy to groom and maintain, requiring little more than brushing during the shedding period. The most common health problems are deafness and progressive blindness (both hereditary conditions) and accidental injury.

This particular breed originated from nineteenth century crosses between British herding dogs and the native dingo, producing a compact, muscular animal with a broad skull and short muzzle (selective breeding), built for intense drive and control of cattle, which later, in the early twentieth century, branched out a more refined strain. These early working dogs were bred solely for function and require high levels of activity and mental stimulation, making them unsuitable for sedentary home life. A new strain emerged in the early twentieth century through the introduction of Dalmatian and Kelpie bloodlines, creating a steadier temperament and a type better suited to be both worker and companion. From this period the breed became known as the Australian Cattle Dog as it was exported worldwide due to its popularity as a working dog. Both strains, working dog and companion, continue to be bred today. The breed is also employed successfully as a guide and assistance dog for people with disabilities, though it still requires substantial physical and mental stimulation to maintain a healthy balance.

The Australian Cattle Dog has been nicknamed a "Red Heeler" or "Blue Heeler" on the basis of its colouring and practice of moving reluctant cattle by nipping at their heels. The nickname "Queensland Heeler" may have originated in a popular booklet, published in Victoria.

There are two distinct forms of the Australian Cattle Dog: the refined twentieth century strain developed after the inclusion of Dalmatian and Kelpie bloodlines, and the older nineteenth century working strain that has remained largely unchanged from the widely successful cross breed of breed of dingo and English Collie (Highland or Smithfield).

Prospective owners should understand the distinction between the two types considering this breed, to distinguish between them and take the time to reflect throughout further documentation. It appears that the lighter type being more adaptable as a companion and also bred for the purpose of exhibitions as in the early stages of its development, as city owners began to favour the appearance of this country breed, being to them of interest at the time (around the 1890s).

The modern strain of ACD is the one most commonly seen in urban environments. It is a medium sized, short coated dog with a compact, balanced outline and smooth curves through the body. The head is finer in proportion rather than broad with a rounded top, a gentle stop between the eyes and a finer, more delicate muzzle that gives a balanced and refined appearance. The coat is close and, to a degree, weather resistant, rather than coarse. The ears are pricked, of medium size, and set well apart; the eyes are oval and dark with a keen, intelligent expression. The overall impression is of an alert, athletic dog capable of endurance and quick bursts of speed.

The nineteenth century working strain remains common in rural Australia, representing an estimated forty percent of the national population. These dogs are sturdier in frame, with thicker bone, a boxier head, a strong jawline, and a dense double coat providing protection from rain and scrub. Some display a small white star on the top of the head, reminiscent of the Bentley mark, a feature linked to the refinement of this strain during the late nineteenth century. Their square build, clear stop between the eyes, deep powerful muzzle, and heavier musculature reflect selection for toughness and stamina rather than refinement. This traditional form continues to be favoured by stockmen for demanding cattle work in rough conditions, although its appearance has also become the preferred style in modern dog shows.