Speaking about the largest pet dog in the world, often we get confused about the criteria that should be taken into consideration. Should we call the tallest dog the largest or is it the heaviest dog that should be regarded the largest? The answer depends on how you decide a dog to be the largest. In the Guinness Book of World Records, there are individual categories for each of them. The Largest In 1989, Zorba, an English Mastiff was considered to be the largest dog in the world with a record-breaking weight of 343 pounds. Unfortunately, he died at the age of eight years and is no longer included in the Guinness book. If Zorba was alive, there is no wonder that he would have been the largest and longest dog ever recorded till date. The official largest living dog in the world according to the Guinness Book of World Records, 2001 is Hercules, an English Mastiff. He weighs 282 pounds and has a 38-inch neck. The owner of Hercules is John Flynn from Peabody, Massachusetts. It was nine year old David DeLauri of Lynn, MA, who actually noticed a large Mastiff who looks like Hercules in the Guinness Book, and later pointed out that Hercules is a record breaker. When Flinn contacted the organization, he found that the previous Mastiff was deceased. Later, it was notified that Hercules won the record of the largest dog in the world. The world's heaviest dog is Kell, again an English Mastiff, from United Kingdom, who weighed 286 pounds at the age of two. Since his neck measured 32 inches, Kell was recorded as the heaviest dog, but not the largest. During an interview, the proud owner, Tom Scott, stated that Kell needs 100 pounds of beef and several gallons of goat's milk every week. Another English Mastiff, Moose, from Vernon , New Jersey was in fact the heaviest dog with a whopping weight of 291 pounds. However, he died shortly, which left Kell as the ultimate winner of the world's heaviest dog. The Tallest The world's tallest dog is the seven feet-tall Gibson, a Harlequin Great Dane. The proud owner of Gibson is Sandy Hall from Grass Valley, California. Gibson is 42.2 inches when standing on all fours. The previous recorded tallest dog was Harvey, with a height of 41.5 inches. Along with the record of the world's tallest dog, Gibson is also the tallest Great Dane and the tallest therapy dog. These are some of the interesting extremes of dog sizes. Even though every dog is not a world record breaker, he does hold a special place in the heart of his human. Small or big, he remains the most courageous and faithful companion for everyone.