Zorba, an English Mastiff from London, holds the all time Guinness World Record for the largest dog ever at 343 lbs. He was also measured from his nose to the tip of his tail at 8 feet, 3 inches and 37 inches at the shoulder. He was 8 years old at the time of the measurements, which was in November 1989. If Zorba was still alive today, there is little doubt that he would still hold the record in the Guinness Book as the largest dog in the world.