However, the Guinness World Record for the smallest dog (not specifically Yorkshire Terrier) is held by Miracle Milly, a chihuahua from Puerto Rico. She measured just 9.65 cm (3.8 inches) tall in 2013.
While there might be Yorkies even smaller than Milly, it's impossible to confirm without a record-keeping system for this specific breed.
It's important to remember that size isn't everything when it comes to pets. It's more important to choose a dog that fits your lifestyle and has a healthy personality, regardless of its size.