The Beagle is a breed of medium-sized dog. A member of the Hound Group, it is similar in appearance to the Foxhound but smaller, with shorter legs and longer, softer ears. Beagles are scent hounds, developed primarily for tracking hare, rabbit, and other game. They have a keen sense of smell and tracking instinct that sees them employed as detection dogs for prohibited agricultural imports and foodstuffs in quarantine around the world. They are popular as pets because of their size, even temper, and lack of inherited health problems. These characteristics also make them the dog of choice for animal testing.

Although beagle-type dogs have existed for over 2,000 years, the modern breed was developed in Britain around the 1830s from several breeds, including the Talbot Hound, the North Country Beagle, the Southern Hound, and possibly the Harrier.

Beagles have been depicted in popular culture since Elizabethan times in literature and paintings, and lately in film, television and comic books. Snoopy of the comic strip Peanuts has been promoted as "the world's most famous beagle".

Early beagle-type dogs

Dogs of similar size and purpose to the modern Beagle can be traced back to around the 5th century BC. Xenophon, born around 433 BC, in his Treatise on Hunting refers to a hound that hunted hares by scent and was followed on foot. Dogs of this type were taken to Rome and may have been imported to Roman Britain. Small hounds are mentioned in the Forest Laws of Canute which exempted them from the ordinance which commanded that all dogs capable of running down a stag should have one foot mutilated. If genuine, Canute's laws would confirm that beagle-type dogs were present in England before 1016, but it is likely they were written in the Middle Ages to give a sense of antiquity and tradition to Forest Law.

From medieval times, beagle was used as a generic description for the smaller hounds, though these dogs differed considerably from the modern breed. Miniature breeds of beagle-type dogs were known from the times of Edward II and Henry VII, who both had packs of Glove Beagles, so named since they were small enough to fit on a glove, and Queen Elizabeth I kept a breed known as a Pocket Beagle, which stood 8 to 9 inches (20 to 23 cm) at the shoulder. Small enough to fit in a "pocket" or saddlebag, they rode along on the hunt. The larger hounds would run the prey to ground, then the hunters would release the small dogs to continue the chase through underbrush. Elizabeth I referred to the dogs as her singing beagles and often entertained guests at her royal table by letting her Pocket Beagles cavort amid their plates and cups.Jesse (1858) pp.438–9 Nineteenth-century sources refer to these breeds interchangeably and it is possible that the two names refer to the same small variety. In George Jesse's Researches into the History of the British Dog from 1866, the early 17th century poet and writer Gervase Markham is quoted referring to the Beagle as small enough to sit on a man's hand and to the: bquote: little small mitten-beagle, which may be companion for a ladies kirtle, and in the field will run as cunningly as any hound whatere, only their musick is very small like reeds. Standards for the Pocket Beagle were drawn up as late as 1901; these genetic lines are now extinct, although modern breeders have attempted to recreate the variety.