The American Bulldog is a breed of working dog developed for catching livestock and for protecting property. Though larger in size, they are the closest surviving relative of the Old English Bulldog because they were not altered to as great an extent while in  Colonial America as their European cousins. There are generally considered to be two types of American Bulldog, the Johnson type and the Scott type, named after the breeders who were influential in developing them, John D. Johnson and Allen Scott. These are more commonly known as Classic or Bully type and Standard or Performance type.

The American Bulldog is a stocky, strong-looking dog. Its coat is short and either white, white with patches, black and white brindle, fawn and white, fawn and white brindle or a combination of all of these. The color comformation is quite varied, but white must be somewhere in the coat for the dog to be confirmed in most ABD clubs. The Johnson type is a larger dog with a shorter muzzle than the Scott type. However, many modern American Bulldogs are a combination of the two types. In general, American Bulldogs weigh between 27 to 57 kg (60 to 125 lb) and are 52 to 70 cm (20 to 28 in) at the withers.