The tallest dog on record as of 2014 is a Great Dane who measures 44 inches at the withers, according to the Guinness Book of World Records. The Great Dane, named Zeus, displaced the former record holder, also a Great Dane, who measured 43 inches at the withers.
Occasionally, English mastiffs have been reported as weighing over 280 pounds, according to CNN. The Guinness Book of World Records doesn't officially track the world's heaviest dog anymore. The Guinness Book of World Records says the largest dog ever was an extinct species known as Hayden's Bone Crushing Dog, which is estimated to have weighed around 370 pounds.