The Cavalier King Charles Spaniel is a small breed of spaniel classed in the toy group of The Kennel Club and the American Kennel Club that originated in the United Kingdom. Since 2000, it has grown in popularity in the United States and ranks as the 17th most popular pure-breed in the United States. It has a silky, smooth coat and commonly a smooth undocked tail. The breed standard recognises four colours: Blenheim (chestnut and white), tricolour (black/white/tan), black and tan, and ruby. The breed is generally friendly, placid, and good with both children and other animals; however, they require much human interaction. Since they are family dogs, it is recommended to not leave one alone for long periods at a time. The expected lifespan of a Cavalier King Charles Spaniel is between nine and 14 years.The Cavalier King Charles changed dramatically in the late 17th century, when it was interbred with flat-nosed breeds. Until the 1920s, the Cavalier shared the same history as the smaller King Charles Spaniel. (The King Charles Spaniel, also known as the English Toy Spaniel, is a completely separate breed than the Cavalier 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.
During that period, Cavaliers were the king's supporters.