The Cavalier King Charles Spaniel is a small spaniel classed as a toy dog by The Kennel Club and the American Kennel Club, that originated in the United Kingdom. It has a silky, smooth coat and commonly a smooth undocked tail. It was bred as a companion dog. Until the 1920s, the Cavalier shared the same history as the smaller King Charles Spaniel. Breeders attempted to recreate what they considered to be the original configuration of the breed, a dog resembling Charles II's King Charles Spaniel of the Restoration.

The breed is generally friendly, affectionate and good with both children and other animals and breeds of dog, but requires a lot of human interaction. Being a family-oriented dog, leaving them alone for long periods of time is discouraged.

An urban legend claims that Charles II issued a special decree granting King Charles Spaniels permission to enter any establishment in the UK, overriding "no dog except guide dogs" rules. A variant of this myth relates specifically to the Houses of Parliament. This myth is sometimes instead applied to the Cavalier King Charles Spaniel. The website for the UK Government disproves this, however.

Cavalier King Charles Spaniels have four coat colours: Blenheim (brown/chestnut and white), black and tan (black and brown), ruby (solid brown), and tricolour (black, white and brown)

Notable characters
Zoe_Trent: A purple Cavalier King Charles Spaniel from Littlest_Pet_Shop.