A Spaniel is a group of gun dog breeds. Spaniels are generally smaller dogs with longer coats and drop ears whose job is to assist with bird hunting. Spaniels have the primary purposes of flushing game from dense undergrowth and retrieving game after it has been shot. Different breeds reflect different emphasis on the dogs' uses. At one time, spaniels were subdivided into Land, Field, and Water spaniels, according to the terrain in which they worked best.

There has been so much interbreeding of various gun dogs over the centuries to achieve additional breeds for new subniches that it is sometimes difficult to determine whether a breed is a spaniel, a retriever, both or neither.

Not much has changed about spaniels in general over the years, as can be seen in this 1921 entry in Collier's New Encyclopedia:

Their distinguishing characteristics are a rather broad muzzle, remarkably long and full ears, hair plentiful and beautifully waved, particularly that of the ears, tail, and hinder parts of the thighs and legs. The prevailing color is liver and white, sometimes red and white or black and white, and sometimes deep brown, or black on the face and breast, with a tan spot over each eye. The English spaniel is a superior and very pure breed. The King Charles is a small variety of the spaniel used as a lapdog. The water spaniels, large and small, differ from the common spaniel only in the roughness of their coats, and in uniting the aquatic propensities of the Newfoundland dog with the fine hunting qualities of their own race. Spaniels possess a great share of intelligence, affection, and obedience, which qualities, combined with much beauty, make them highly prized as companions.