Irish, also known as Irish Gaelic or simply Gaelic, is a Goidelic language of the Insular Celtic branch of the Celtic language group, which is a part of the Indo-European language family. Irish is indigenous to the island of Ireland and was the population's first language until the 19th century, when English gradually became dominant, particularly in the last decades of the century. Today, Irish is still commonly spoken as a first language in areas of Ireland collectively known as the Gaeltacht, in which only 2% of Ireland's population lived in 2022.

The Goidelic or Gaelic languages form one of the two groups of Insular Celtic languages, the other being the Brittonic languages.