Hercules: The World's Biggest Dog Ever According to Guinness World Records Hercules was recently awarded the honorable distinction of Worlds Biggest Dog by Guinness World Records. Hercules is an English Mastiff and has a 38 inch neck and Weighs 282 pounds. With "paws the size of softballs" (reports the Boston Herald), the three-year-old monster is far larger and heavier than his breed's standard 200lb. limit. Hercules owner Mr. Flynn says that Hercules weight is natural and not induced by a bizarre diet: "I fed him normal food and he just grew".... and grew. and grew. and grew.