The Bretons (Breton: Bretoned, Breton pronunciation: [bre'tonet]) are an ethnic group located in the region of Brittany in France. They trace much of their heritage to groups of Brittonic speakers who immigrated from southwestern Great Britain, particularly Cornwall and Devon, to expand their territory onto the continent. They also descend in some parts from Vikings. They migrated in waves from the 3rd to 9th century (most heavily from 450-600) into Armorica, which was subsequently named Brittany after them.

In the late 4th century, large numbers of British auxiliary troops in the Roman army may have been stationed in Armorica. The 9th-century Historia Brittonum states that the emperor Magnus Maximus, who withdrew Roman forces from Britain, settled his troops in the province. Nennius and Gildas mention a second wave of Britons settling in Armorica in the following century to escape the invading Anglo-Saxons and Scoti. Modern archaeology also supports a two-wave migration.  It is generally accepted that the Brittonic speakers who arrived gave the region its current name as well as the Breton language, Brezhoneg, a sister language to Welsh and Cornish.  There are numerous records of Celtic Christian missionaries migrating from Britain during the second wave of Breton colonisation, especially the legendary seven founder-saints of Brittany as well as Gildas. As in Cornwall, many Breton towns are named after these early saints. The Irish saint Columbanus was also active in Brittany and is commemorated accordingly at Saint-Columban in Carnac.  In the Early Middle Ages, Brittany was divided into three kingdoms -- Domnonee, Cornouaille (Kernev), and Bro Waroc'h (Broerec) -- which eventually were incorporated into the Duchy of Brittany. The first two kingdoms seem to derive their names from the homelands of the migrating tribes in Britain, Cornwall (Kernow) and Devon (Dumnonia). Bro Waroc'h ("land of Waroch", now Bro Gwened) derives from the name of one of the first known Breton rulers, who dominated the region of Vannes (Gwened). The rulers of Domnonee, such as Conomor, sought to expand their territory, claiming overlordship over all Bretons, though there was constant tension between local lords.  Bretons were the most prominent of the non-Norman forces in the Norman conquest of England. A number of Breton families were of the highest rank in the new society and were tied to the Normans by marriage. The Scottish Clan Stewart and the royal House of Stuart have Breton origins. Alan Rufus, also known as Alan the Red, was both a cousin and knight in the retinue of William the Conqueror. Following his service at Hastings, he was rewarded with large estates in Yorkshire. At the time of his death, he was by far the richest noble in England. His manorial holding at Richmond ensured a Breton presence in northern England. The Earldom of Richmond later became an appanage of the Dukes of Brittany.

what were the historical origins of the bretons?
In the late 4th century, large numbers of British auxiliary troops in the Roman army may have been stationed in Armorica.