The King Charles Spaniel (also known as the English Toy Spaniel) is a small dog breed of the spaniel type. In 1903, the Kennel Club combined four separate toy spaniel breeds under this single title. The other varieties merged into this breed were the Blenheim, Ruby and Prince Charles Spaniels, each of which contributed one of the four colours available in the breed.
Thought to have originated in the Far East, toy spaniels were first seen in Europe during the 16th century. They were made famous by their association with King Charles II of Great Britain and Ireland (1630–1685) and have been linked with British royalty since the time of Queen Mary I (1516–1558). Members of the breed were owned by Grand Duchess Anastasia Nikolaevna of Russia.
The King Charles Spaniel and the other types of toy spaniels were crossbred with the Pug in the early 19th century to reduce the size of the nose, as was the style of the day. The 20th century saw attempts to restore lines of King Charles Spaniels to the breed of Charles II's time. These included the unsuccessful Toy Trawler Spaniel and the now popular Cavalier King Charles Spaniel. The Cavalier is slightly larger, with a flat head and a longer nose, while the King Charles is smaller, with a domed head and a flat face.
Historically the breeds that were merged into the King Charles Spaniel were used for hunting; due to their stature they were not well suited. They have kept their hunting instincts, but do not exhibit high energy and are better suited to being lapdogs. The modern breed is prone to several health problems, including cardiac conditions and a range of eye problems.