The Bullmastiff is a breed of large dog. A member of the Working Group it is large and solidly built with a short muzzle. The Bullmastiff shares the characteristics of Molosser dogs like it and was originally developed by 19th-century gamekeepers to guard estates and immobilize poachers. The breed's bloodlines are drawn from the English Mastiff and Old English Bulldog; it was recognized as a purebred dog by the English Kennel Club in 1924.