Which language family includes both Irish and Welsh?

Celtic is the language family that includes both Irish and Welsh.

Celtic languages form a branch of the Indo-European family. The modern group is usually divided into Goidelic languages—Irish, Scottish Gaelic, and Manx—and Brittonic languages—Welsh, Breton, and Cornish. This classification reflects historical development rather than mutual intelligibility.

The Celtic languages were once spoken across a much larger area of Europe. Over many centuries, they retreated as Latin and later Germanic languages expanded. Irish and Welsh survived through different historical paths: Irish remains an official language of Ireland and an official language of the European Union, while Welsh has a strong institutional presence in Wales.

The family’s ancient history is reconstructed through inscriptions, manuscripts, place names, and comparison with related Indo-European languages. The term “Celtic” describes linguistic relationship; it does not mean that all Celtic-speaking communities share identical traditions or a single ancient nation.