A legendary king of Celtic Britain, about all that can be said about Old King Cole with any certainty is that:

Old King Cole was a merry old soul
     And a merry old soul was he;
He called for his pipe, and he called for his bowl
     And he called for his fiddlers three.

Every fiddler he had a fiddle,
     And a very fine fiddle had he;
Oh there's none so rare, as can compare
     With King Cole and his fiddlers three

So runs a traditional nursery rhyme. In fact, there are several candidates for a historical King Cole, or Coel.

One may have lived in the third century, and was the eponymous founder of the city of Colchester in Essex, England. "Colchester" means "Cole's castle." These legendary tales are sometimes included with the more familiar tales of King Arthur and his knights in the Matter of Britain. There may have been two rulers of that name in Colchester, a Coel Godhebog, or Cole the Magnificent; and Coel Hen, Cole the Old. Little definite is known of either monarch, or whether there were indeed two Coles, only one, or whether he is purely legendary. Another vein of legend links him to Cunobelinus, Shakespeare's Cymbeline.

Geoffrey of Monmouth lists a King Cole in his Historia Regum Britanniae as a king of the Britons following the reign of King Asclepiodotus. The Welsh chronicles state further that his name was Coel Hen Godhebog, which would integrate the two possible names together. Monmouth states that Coel, upset with Asclepiodotus's handling of Diocletian's massacres, began a rebellion in the duchy of Kaelcolim (Colchester), of which he was duke. He met Asclepiodotus in battle and killed him, thus taking the kingship of Britain upon himself. Rome, apparently, was thrilled that Britain had a new king and sent a senator, Constantius Chlorus, to act as a diplomat to Coel. Afraid of the Romans, Coel met Constantius and agreed to pay tribute and submit to Roman laws as long as he was allowed to retain the kingship of Britain. Constantius agreed to these terms but one month later, Coel died. Constantius took Coel's daughter, Helena, and crowned himself as Coel's successor. Helen later gave birth to a son who became Emperor Constantine the Great. Note that the Historia Regum Britanniae is not generally considered historically accurate.

Yet another possibility is that Cole is the Celtic deity Camulus, god of war. The old name of Colchester was Camulodunum, and the derivation sequence /kamul/ (+ lenition) > /kawul/ > /kaul/ > /ko:l/ is not impossible, especially among the Celtic languages. If Camulus is Cole, then Colchester (from the Latin for "Cole's fortress") and Camulodunum (from Brythonic Celtic for "the fortress of Camulus") are synonyms; it is likely that the Latin form is a calque on the Celtic.

Colchester contains an old Roman quarry that is called "King Cole's Kitchen". The word ceol means music in Gaelic, and this may be the origin of the rhyme about Cole and his fiddlers.

David Nash Ford and Peter L Kessler contend that Cole was Coel Hen, High King of Northern Britain who apparently lived around AD 350-420, during the time when the Romans withdrew their forces from Britain. He may have been the last of the Roman Duces Brittanniarum (Dukes of the Britons), and took over the northern capital at Eburacum (York) to rule over what had been the northern province of Roman Britain. Most of the Celtic British kings of north Britain, and many Welsh kings, would trace their descent from him - for example Rheged.

Some think that it is unlikely that the nursery rhyme was written before 1585, when Sir Walter Raleigh introduced tobacco into England. Others think that the "pipe" referred to may not have been a smoking pipe, but rather a musical instrument.

In the United States, King Coal is sometimes invoked as a metaphor for the centrality of coal mining in the economy of Appalachia, a role similar to that played by King Cotton in the Deep South

In Canada, King Cole is a brand of tea which has been manufactured by G.E. Barbour Inc for about a century.