Breton literature may refer to literature in the Breton language (Brezhoneg) or the broader literary tradition of Brittany in the three other main languages of the area, namely, Latin, Gallo and French – all of which have had strong mutual linguistic and cultural influences. Breton literature can be categorised into an Old Breton period, from the 5th to 11th century; and a Middle Breton period, up to the 17th century. The period break is marked by the Norman invasions of the 10th and 11th centuries which triggered an exodus out of Brittany.
The oldest surviving manuscript in the Breton language (dating to the end of the 8th Century) is kept in Leyden University, Netherlands, and predates by more than a century the oldest text referenced in French. It is generally assumed by specialists that this is the most ancient text in a continental Brythonic language and was studied by the late Professor Léon Fleuriot (1923–1987). The manuscript itself is a fragment of medicinal recipes composed of plants suggesting that Breton may well have been used by people of learning at the turn of the 11th century.
Although written in French the Breton Gospel (British Library, Egerton 609) is an important literary work in terms of the wider scope of Breton culture. Amongst other things it attests to a high degree of learning and, presumably, monasterial wealth in Brittany comparable to that of Lindisfarne and Kells. The Gospel Book manuscript dating from the 9th century contains the Latin text of the four Gospels, along with prefatory material and canon tables – an interesting admixture of traditions.
Another early known piece of Breton literature is found in the margins of a 14th-century Latin manuscript, scribbled by a scribe weary of his toil and mind on more immediate concerns, he left for posterity a four line love poem, the first two lines beginning: The main principle of Breton poetry is that the next to last syllable in a line should rhyme with one or more other syllables in the same line. For example, in the first line above, “en” is the second to last syllable, which rhymes with “guen” and “heguen”.
There are several texts from the 15th and 16th century: Before the literary revival movement promoted by Gwalarn in the early 20th century, most literature in Breton consisted of religious writings. Jean-François Le Gonidec (Breton: Yann-Frañsez ar Gonideg) (1775 – 1838) played an important role in Breton literature by initiating a reform of Breton orthography, producing an orderly grammar and making the first Breton translation of the New Testament.