Mastiff may refer to: Dog breeds Molosser, a group of several breeds of dog also known as Mastiffs. Alpine Mastiff, an extinct breed originating in Switzerland. Bullmastiff, said to be a cross between the English Mastiff and the Bulldog. English Mastiff, a breed of dog in the Molosser group originating in England. German Mastiff, a breed of dog originating in Germany American Mastiff, a breed of dog originating in the United States South African Mastiff, a breed of dog originating in South… (More on Mastiff)