NENNIUS (fl. 796), a Welsh writer to whom we owe the Historia Britonum, lived and wrote in Brecknock or Radnor. His work is known to us through thirty manuscripts; but the earliest of these cannot be dated much earlier than the year 1000; and all are defaced by interpolations which give to the work so confused a character that critics were long disposed to treat it as an unskilful forgery. A new turn was given to the controversy by Heinrich Zimmer, who, in his Nennius vindicatus (1893), traced the history of the work and, by a comparison of the manuscripts with the 11th-century translation of the Irish scholar, Gilla Coemgim (d. 1072), succeeded in stripping off the later accretions from the original nucleus of the Historia. Zimmer follows previous critics in rejecting the Prologus maior (§§ 1, 2), the Capitula, or table of contents, and part of the Mirabilia which form the concluding section. But he proves that Nennius should be regarded as the compiler of the Historia proper (§§ 7-65). Zimmer’s conclusions are of more interest to literary critics than to historians. The only part of the Historia which deserves to be treated as a historical document is the section known as the Genealogiae Saxonum (§§ 57-65). This is merely a recension of a work which was composed about 679 by a Briton of Strathclyde. The author’s name is unknown; but he is, after Gildas, our earliest authority for the facts of the English conquest of England. Nennius himself gives us the oldest legends relating to the victories of King Arthur; the value of the Historia from this point of view is admitted by the severest critics. The chief authorities whom Nennius followed were Gildas' De excidio Britonum, Eusebius, the Vita Patricii of Murichu Maccu Machtheni, the Collectanea of Tirechan, the Liber occupationis (an Irish work on the settlement of Ireland), the Liber de sex aetatibus mundi, the chronicle of Prosper of Aquitaine, the Liber beati Germani. The sources from which he derived his notices of King Arthur (§ 56) have not been determined.

See J. Stevenson’s edition of the Historia Britonum (English Hist. Soc., 1838), based on a careful study of the MSS.; A. de la Borderie, L’Historia Britonum (Paris and London, 1883), which summarizes the older negative criticism; H. Zimmer, Nennius vindicatus (Berlin, 1893): T. Mommsen in Neues Archiv der Gesellschaft für ältere deutsche Geschichtskunde, xix. 283.  (H. W. C. D.)