Celtic languages are languages that are spoken by people in Ireland, Scotland, Wales, and Brittany (a region in France). They are very old languages, with some of them being around for thousands of years. People who speak these languages often have a lot in common, like a shared culture and history. Even though the languages themselves may sound very different, they usually have a lot of similar words and grammar. The most common Celtic languages today are Irish, Scots Gaelic, Manx (from the Isle of Man), Welsh, and Breton.