Historia Regum Britanniae

The Historia Regum Britanniae (English: The History of the Kings of Britain) is a pseudohistorical account of British history, written c. 1136 by Geoffrey of Monmouth. It chronicles the lives of the kings of the Britons in a chronological narrative spanning a time of two thousand years, beginning with the Trojans founding the British nation and continuing until the Anglo-Saxons assumed control of much of Britain around the 7th century. It is one of the central pieces of the Matter of Britain.

Although credited uncritically well into the 16th century, since the 17th century it has been credited with little value as history – when events described, such as Julius Caesar's invasions of Britain, can be corroborated from contemporary histories, Geoffrey's account can be seen to be wildly inaccurate – but it remains a valuable piece of medieval literature, which contains the earliest known version of the story of King Lear and his three daughters, and introduced non-Welsh-speakers to the legend of King Arthur.