A number of mainland Europe tribes that invaded the British Isles between 1000 and 500 B.C. The Celts settled throughout the Isles and eventually became the races known as Britons, Welsh, Scots, Irish, and Cornish.
Control of the British Isles was taken from the Celtic tribes when the Romans invaded in the first century. The Celts known as the Britons, who inhabited the southern half of the island, became "Romanized" and were thus left as the ruling race after the Romans withdrew. Arthur is often represented as a member (leader) of this race.
However, the term Celt must be regarded as linguistic and cultural, rather than racial.
In the strictly academic context of Celtic studies, the term Celtic literature is used by Celticists to denote any number of bodies of literature written in a Celtic language, encompassing the Irish, Welsh, Cornish, Manx, Scottish Gaelic and Breton languages in either their modern or earlier forms.
Alternatively, the term is often used in a popular context to refer to literature which is written in a non-Celtic language, but originates nonetheless from the Celtic nations or else displays subjects or themes identified as "Celtic". Examples of these literatures include the medieval Arthurian romances written in the French language, which drew heavily from Celtic sources, or in a modern context literature in the English language by writers of Irish, Welsh, Cornish, Manx, Scottish or Breton extraction. Literature in Scots and Ulster Scots may also be included within the concept. In this broader sense, the applicability of the term "Celtic literature" can vary as widely as the use of the term "Celt" itself.
Celtic Church | The Legend of King Arthur