The English Cocker Spaniel is a breed of gun dog. It is noteworthy for producing one of the most varied numbers of pups in a litter among all dog breeds. The English Cocker Spaniel is an active, good-natured, sporting dog standing well up at the withers and compactly built. There are "field" or "working" cockers and "house" cockers. It is one of several varieties of spaniel and is the foundation of its American cousin, the American Cocker Spaniel. The English Cocker is closer to the working-dog form of the Field Spaniel and the English Springer Spaniel. English Cocker Spaniels are also known as the "Merry Spaniel" due to their constantly wagging tail.

Gun dogs or bird dogs are types of hunting dogs developed to assist hunters in finding and retrieving game, typically various fowls that are shot down on the flight. The term hunting dog is broad and includes all breeds and skills of hunting canines, but "gun dogs" refers to canines that are trained to work alongside a loud firearm while hunting or retrieving game. Gun dogs are divided into three main categories: pointers and retrievers, setters and spaniels, and water dogs.