Celtic Britons

The Britons (*Pritanī, Latin: Britanni, Welsh: Brythoniaid), also known as Celtic Britons or ancient Britons, were the Celtic people who inhabited Great Britain from at least the British Iron Age until the High Middle Ages, at which point they diverged into the Welsh, Cornish, and Bretons (among others). They spoke Common Brittonic, the ancestor of the modern Brittonic languages.

The earliest written evidence for the Britons is from Greco-Roman writers and dates to the Iron Age. Ancient Britain was made up of many tribes and kingdoms, associated with various hillforts. The Britons followed an ancient Celtic religion overseen by druids. Some of the southern tribes had strong links with mainland Europe, especially Gaul and Belgica, and minted their own coins. The Roman Empire conquered most of Britain in the 1st century AD, creating the province of Britannia. The Romans invaded northern Britain, but the Britonnic tribes such as the Caledonians and Picts in the north remained unconquered, and Hadrian's Wall which bisects modern Northumbria and Cumbria became the edge of the empire. A Romano-British culture emerged, mainly in the southeast, and British Latin coexisted with Brittonic. It is unclear what relationship the Britons had with the Picts, who lived outside of the empire in northern Britain; however, most scholars today accept the fact that the Pictish language was closely related to Common Brittonic.

Following the end of Roman rule in Britain during the 5th century, Anglo-Saxon settlement of eastern and southern Britain began. The culture and language of the Britons gradually fragmented, and much of their territory gradually became Anglo-Saxon, while the north and the Isle of Man became subject to a similar settlement by Gaelic-speaking tribes from Ireland who would eventually form Scotland. The extent to which this cultural change was accompanied by wholesale population changes is still debated. During this time, Britons migrated to mainland Europe and established significant colonies in Brittany (now part of France), the Channel Islands, and Britonia (now part of Galicia, Spain). By the 11th century, Brittonic-speaking populations had split into distinct groups: the Welsh in Wales, the Cornish in Cornwall, the Bretons in Brittany, the Cumbrians of the Hen Ogledd ("Old North") in modern southern Scotland and northern England, and the remnants of the Pictish people in northern Scotland. Common Brittonic developed into the distinct Brittonic languages: Welsh, Cumbric, Cornish and Breton.

In Celtic studies, 'Britons' refers to native speakers of the Brittonic languages in the ancient and medieval periods, "from the first evidence of such speech in the pre-Roman Iron Age, until the central Middle Ages".

The earliest known reference to the inhabitants of Britain was made by Pytheas, a Greek geographer who made a voyage of exploration around the British Isles between 330 and 320 BC. Although none of his writings remain, writers during the following centuries make frequent reference to them. The ancient Greeks called the people of Britain the Pretanoí or Bretanoí. Pliny's Natural History (77 AD) says the older name for the island was Albion, and Avienius calls it insula Albionum, "island of the Albions".The name could have reached Pytheas from the Gauls.

The P-Celtic ethnonym has been reconstructed as *Pritanī, from Common Celtic *kʷritu, which became Old Irish cruth and Old Welsh pryd. This likely means "people of the forms, shapely people", and could be linked to the Latin name Picti (the Picts), which is usually explained as meaning "painted people". The Old Welsh name for the Picts was Prydyn. Linguist Kim McCone suggests the name became restricted to inhabitants of the far north after Cymry displaced it as the name for the Welsh and Cumbrians. The Welsh prydydd, "maker of forms", was also a term for the highest grade of a bard.

The medieval Welsh form of Latin Britanni was Brython (singular and plural). Brython was introduced into English usage by John Rhys in 1884 as a term unambiguously referring to the P-Celtic speakers of Great Britain, to complement Goidel; hence the adjective Brythonic refers to the group of languages. "Brittonic languages" is a more recent coinage (first attested in 1923 according to the Oxford English Dictionary).

In the early Middle Ages, following the Anglo-Saxon settlement of Britain, the Anglo-Saxons called all Britons Bryttas or Wealas (Welsh), while they continued to be called Britanni or Brittones in Medieval Latin. From the 11th century, they are more often referred to separately as the Welsh, Cumbrians, Cornish, and Bretons, as they had separate political histories from then. From the early 16th century, and especially after the Acts of Union 1707, the terms British and Briton could be applied to all inhabitants of the Kingdom of Great Britain, including the English, Scottish, and some Irish, or the subjects of the British Empire generally.