The Staffordshire Bull Terrier, also called the Staffy or Stafford, is a purebred dog of small to medium size in the terrier group that originated in the northern parts of Birmingham and in the Black Country of Staffordshire, for which it is named. They descended from 19th-century bull terriers that were developed by crossing bulldogs with various terriers to create a generic type of dog generally known as bull and terriers. Staffords share the same ancestry with the modern Bull Terrier, although the two breeds developed along independent lines, and do not resemble each other. Modern Staffords more closely resemble the old type of bull terrier, and were first recognised as a purebred dog breed by The Kennel Club of Great Britain in 1935.

Terrier is a type of dog originally bred to hunt vermin. A terrier is a dog of any one of many breeds or landraces of the terrier type, which are typically small, wiry, game, and fearless. There are five different groups of terrier, with each group having different shapes and sizes.