Hercules-World Largest Dog - Hercules World's Biggest Dog ever according to Guinness World Records.Hercules was recently awarded the honorable distinction of World's Biggest Dog by Guinness Records, Hercules is an English Mastiff and has 38 Inch Neck and weighs 282 Pounds. Hercules owner Mr Flynn says that Hercules weight is natural and not induced by a bizarre diet: 'I fed him normal food and he jusy grew'....and grew and grew and grew!!!!!!