Irish (Standard Irish: Gaeilge), also known as Irish Gaelic or simply Gaelic (/ˈɡeɪlɪk/ GAY-lik), is a Goidelic language of the Insular Celtic branch of the Celtic language family, 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 total number of people (aged 3 and over) in Ireland who claimed they could speak Irish in April 2022 was 1,873,997, representing 40% of respondents, but of these, 472,887 said they never spoke it and a further 551,993 said they only spoke it within the education system. Linguistic analyses of Irish speakers are therefore based primarily on the number of daily users in Ireland outside the education system, which in 2022 was 20,261 in the Gaeltacht and 51,707 outside it, totalling 71,968. In response to the 2021 census of Northern Ireland, 43,557 individuals stated they spoke Irish on a daily basis, 26,286 spoke it on a weekly basis, 47,153 spoke it less often than weekly, and 9,758 said they could speak Irish, but never spoke it. From 2006 to 2008, over 22,000 Irish Americans reported speaking Irish as their first language at home, with several times that number claiming "some knowledge" of the language.
For most of recorded Irish history, Irish was the dominant language of the Irish people, who took it with them to other regions, such as Scotland and the Isle of Man, where Middle Irish gave rise to Scottish Gaelic and Manx. It was also, for a period, spoken widely across Canada, with an estimated 200,000–250,000 daily Canadian speakers of Irish in 1890. On the island of Newfoundland, a unique dialect of Irish developed before falling out of use in the early 20th century.
With a writing system, Ogham, dating back to at least the 4th century AD, which was gradually replaced by Latin script since the 5th century AD, Irish has one of the oldest vernacular literatures in Western Europe. On the island, the language has three major dialects: Connacht, Munster and Ulster Irish. All three have distinctions in their speech and orthography. There is also a "standard written form" devised by a parliamentary commission in the 1950s. The traditional Irish alphabet, a variant of the Latin alphabet with 18 letters, has been succeeded by the standard Latin alphabet (albeit with 7–8 letters used primarily in loanwords).
Irish has constitutional status as the national and first official language of the Republic of Ireland, and is also an official language of Northern Ireland and among the official languages of the European Union. The public body Foras na Gaeilge is responsible for the promotion of the language throughout the island. Irish has no regulatory body but the standard modern written form is guided by a parliamentary service and new vocabulary by a voluntary committee with university input.