The King Charles Spaniel (known as the English Toy Spaniel in the U.S. and Canada) is a small breed of dog in the spaniel category. The Cavalier King Charles Spaniel is a different breed, although it is also sometimes referred to as a King Charles Spaniel.

The breed originated in Renaissance-era Great Britain as a companion dog for royalty, although in that era the breed more closely resembled the modern Cavalier King Charles Spaniel than contemporary English Toys. Crosses between long-snouted toy spaniels and short-snouted breeds such as the Pug or Japanese Chin in the 18th and 19th centuries led to the breed's current appearance.