The Bullmastiff is a large, powerfully built working dog breed developed in 19th-century England by crossing the English Mastiff with the Old English Bulldog. Originally known as the "Gamekeeper's Night Dog," they were bred to quietly track, tackle, and pin down poachers on country estates without mauling them. Today, they are celebrated as docile, deeply affectionate family guardians who are fiercely loyal to their households.