Shakespeare's play is based on various accounts of the semi-legendary Brythonic figure Leir of Britain, whose name has been linked by some scholars to the Brythonic god Lir/Llŷr, though in actuality the names are not etymologically related. Shakespeare's most important source is probably the second edition of The Chronicles of England, Scotlande, and Irelande by Raphael Holinshed, published in 1587. Holinshed himself found the story in the earlier Historia Regum Britanniae by Geoffrey of Monmouth, which was written in the 12th century. Edmund Spenser's The Faerie Queene, published 1590, also contains a character named Cordelia, who also dies from hanging, as in King Lear.
Other possible sources are the anonymous play King Leir (published in 1605); The Mirror for Magistrates (1574), by John Higgins; The Malcontent (1604), by John Marston; The London Prodigal (1605); Montaigne's Essays, which were translated into English by John Florio in 1603; An Historical Description of Iland of Britaine (1577), by William Harrison; Remaines Concerning Britaine (1606), by William Camden; Albion's England (1589), by William Warner; and A Declaration of egregious Popish Impostures (1603), by Samuel Harsnett, which provided some of the language used by Edgar while he feigns madness. King Lear is also a literary variant of a common folk tale, Love Like Salt, Aarne–Thompson type 923, in which a father rejects his youngest daughter for a statement of her love that does not please him.
The source of the subplot involving Gloucester, Edgar, and Edmund is a tale in Philip Sidney's Countess of Pembroke's Arcadia (1580–90), with a blind Paphlagonian king and his two sons, Leonatus and Plexitrus.
Changes from source material
Besides the subplot involving the Earl of Gloucester and his sons, the principal innovation Shakespeare made to this story was the death of Cordelia and Lear at the end; in the account by Geoffrey of Monmouth, Cordelia restores Lear to the throne, and succeeds him as ruler after his death. During the 17th century, Shakespeare's tragic ending was much criticised and alternative versions were written by Nahum Tate, in which the leading characters survived and Edgar and Cordelia were married (despite the fact that Cordelia was previously betrothed to the King of France). As Harold Bloom states: "Tate's version held the stage for almost 150 years, until Edmund Kean reinstated the play's tragic ending in 1823."