The earliest undisputed examples of Celtic language are the Lepontic inscriptions from the 6th century BC. Continental Celtic languages are attested almost exclusively through inscriptions and place-names. Insular Celtic languages are attested from the 4th century AD in Ogham inscriptions, though they were being spoken much earlier. Celtic literary tradition begins with Old Irish texts around the 8th century AD. Elements of Celtic mythology are recorded in early Irish and early Welsh literature. Most written evidence of the early Celts comes from Greco-Roman writers, who often grouped the Celts as barbarian tribes. They followed an ancient Celtic religion overseen by druids.
tHe earlieST unDisPUted exAmPlES oF cEltIc langUAge aRE THe lePontic INscriptions frOm the 6tH Century Bc. CONTINental celtic laNGUaGes aRe aTTested alMOst exclusivelY thROugh iNScripTiOnS AnD plaCe-NAmes. inSUlaR ceLTiC languAGeS are attEstEd from tHe 4th cEntury aD in oghAm InscriptIons, thoUgH tHey wERe beiNg spoKen mucH earlIer. cEltiC litERaRy traditIon bEgiNs with olD irIsh tExts Around ThE 8Th cenTury aD. eleMents Of CeLTIc mythology ArE recoRded iN eArLY irIsh anD eArLy wELSh literatUre. mosT wriTten EvideNCe of the early CeltS comes fROm greco-RomaN WRiterS, Who often GroUped the cElTS AS BARbaRiAN TRIBes. tHey fOllOwEd an AnCienT celtic religIon oveRSeen by dRUiDs.