Animal Doctor USA

TobyKeith, seen above, was born on January 9, 2001. At 21 years, 66 days old, the darling Chihuahua was verified as the world's oldest living dog. He lives in Greenacres, Florida with two other dogs and two parrots, including an Umbrella Cockatoo named Coco with whom TobyKeith spends much of his time. From Guinness World Records:

TobyKeith's owner, Gisela Shore, has been with him for the vast majority of his life, after adopting him from an animal shelter when he was just a few months old. 

"I was a volunteer at Peggy Adams Animal Rescue and one of the employees told me about an elderly couple trying to surrender a puppy because they could not take care of him any longer," said Gisela[…]

The oldest dog ever recorded was an Australian cattle-dog named Bluey, owned by Les Hall of Rochester, Victoria, Australia. 

Bluey was obtained as a puppy in 1910 and worked among cattle and sheep for nearly 20 years before being put to sleep on 14 November 1939 aged 29 years 5 months.