Meet the Worlds Oldest Dog. A 21-Year-Old Chihuahua that lives here in Palm Beach, in Wellington Florida. The tan colored pooch whose name is Toby Keith has been recognized by Guinness as the oldest dog in the world. The pups owner adopted him as a puppy from a local shelter. She says "that he is in perfect health and enjoys walks to the park, drives in the car, and sunbathing."