When did the celts die out?

The Celts did not die out. The Irish and Scottish ethnic groups are among modern Celtic peoples.

The Celts, did not die out. The modern Celts, are the Irish, Scottish, Welsh, Manx, Britons and the Cornish. It is believed that 15-20% of England has Celtic heritage. There are even some Celtic descents around mainland Europe, including Italy or France, or even at some point Asia Minor. I am an Irish Australian, and I consider myself Gaelic and Celtic.