Geoffrey Of Monmouth, an old English chronicler, born about 1100, died about 1154. He is supposed to have received his education in the Benedictine monastery near Monmouth, where he compiled his Chronicon she Historia Britonum, to which he probably owed his promotion in 1152 to the see of St. Asaph. Geoffrey's chronicle professes to be a translation from an old Welsh manuscript which one Walter Calenius, an archdeacon of Oxford, discovered in Brittany, and which he requested him to render into Latin. That some part of the work is a translation there seems to be no doubt, as its main features agree with the history of Nennius, written several centuries previous; but so numerous are the legends and fables interwoven into it, and so extensive is the period it embraces (from Brut, the great-grandson of Aeneas, to the death of Cadwalla-der or Ceadwalla, king of Wessex, in 688), that its historical value is very inconsiderable. If historians are inclined to doubt the veracity of Geoffrey, the readers of romance are indebted to him for having preserved and perhaps reconstructed the legends of Arthur and his knights.

The work was originally divided into eight books, to which Geoffrey added the book of Merlin's "Prophecies," and was first printed at Paris in 1508. The best recent editions are those of J. A. Giles (1842) and Bolm (1848), both of which are reprints from a translation by Aaron Thompson published in 1718.