The Celts were any people known to have spoken a Celtic language. There is debate about the cultural aspect but generally speaking the Celts occupied The British Isles, Belgium, France, Switzerland, Austria, southern Germany and Germany west of the Rhine, northern Italy and large parts of Spain and Portugal. They were probably also in Slovenia and "Celtic" grave sites have been found as far east as Romania. A breakaway group of Celts invaded Anatolia and set up a kingdom there centred around modern Ankara in Turkey. The region was later known as Galatia and it's people were referred to as Galatians.

The language these people spoke is generally referred to as Gaulish or continental celtic. The language survives only through the insular celtic languages of the British Isles - Irish, Gaelic, Welsh, Breton (spoken in Brittany, France but brought there by people from Britain) and the revived languages of Manx and Cornish. The Celts of Europe adopted Latin over the centuries which developed into French, Spanish, Romanian etc and some adopted germanic languages like Dutch and German.