Gildas, St (c. 500–570)

British saint and historian, author of the history De Excidio et Britanniae Conquestu, the first by a British historian and the only one written about the Celts

Gildas's history was probably compiled between 516 and 547; it stretches from the arrival of the Romans up to the period of writing. It is an unreliable and vague work, written mainly as a moral treatise. It gives no precise dates and is limited to Gildas's own region, the west of Britain. Nevertheless, it is the only contemporary source of events in Britain in the first half of the 6th century and is particularly valuable for its evidence of the Anglo-Saxon invasions.

Little is known of his life; he was a monk and there is a tradition that he was born in Strathclyde, later fled to Wales, and that he also travelled in Ireland and perhaps in Brittany. According to an early life he went on a pilgrimage to Rome about 520.