Which breed of dog is this?

A Shih Tzu (literally 'Xi Shi dog', meaning "lion dog"), is a toy dog breed, weighing from 4 to 7.25 kilograms (9–16 lb) when fully grown. The breed originated on the Tibetan Plateau and was developed in China.

The Shih Tzu is a sturdy little dog with a short muzzle and large dark eyes. They have a soft and long double coat. Although sometimes long, a Shih Tzu will not always have extremely lengthy hair. Some of them have more short, curly hair. This is purely a choice made by the owners.

A Shih Tzu should stand no more than 26.7 cm at the withers and with an ideal weight of 4.5 to 7.3 kg. Floppy ears are covered with long fur, and the heavily furred tail is carried curled over the back. The coat may be of any color, though white and with blazes of grey are frequently seen. A very noticeable feature is the underbite, which is required in the breed standard.

Although an individual Shih Tzu's temperament varies from dog to dog, the breed has a personality and temperament that is loyal, affectionate, outgoing, cute, and alert.

They tend to be possessive around other dogs. Training and proper socializing must start at a young age for the Shih Tzu to obey basic commands, for the Shih Tzu is prone to stubbornness when it comes to training.

The UK Kennel Club survey puts the median lifespan of a Shih Tzu at 13 years and 2 months, with most living 10 to 16 years. The oldest living Shih Tzu was one named Smokey from Florida, who lived to be 23 years old.