Regan is a fictional character in William Shakespeare's tragic play King Lear, named after a King of the Britons recorded by the medieval scribe Geoffrey of Monmouth. Shakespeare based the character on Regan, a personage described by Geoffrey of Monmouth in his pseudo-historical chronicle Historia regum Britanniae ("History of the Kings of Britain", c. 1138) as one of the British king Lear's three daughters, alongside Goneril and Cordelia (the source for Cordelia), and the mother of Cunedagius.