Catholic Encyclopedia: St. Gildas: Biographical entry for St. Gildas the Wise, also called "Badonicus," born to a British family in Scotland, educated in Wales, monk, priest, died in 570.
Gildas: Profile of the saint. With links.
Gildas Badonicus: A commentary by John Morris on the 6th-century author, a summary by Frank Reno of the confusions with others of the same name, the 11th-century and 12th-century lives and the Giles translation of De Excidio Brittaniae et Conquestu.
Gildas the Wise: Biographical profile, by Karen Rae Keck.
Gildas, Saint: Very brief biographical entry in the Columbia Encyclopedia.
St. Gildas Badonicus: Biography by David Nash Ford of the 6th-century author of "De Excidio Britanniae," drawing on the dubious 11th-century life by a monk of Rhuys.
St. Gildas the Wise, or Badonicus, Abbot: From Alban Butler's Lives of the Saints.
Vietnamese Eucharistic Youth Society: St. Gildas: The story of St. Gildas the Wise, suited to children. Preformatted line breaks can make this difficult to read.