The Irish people ( , na hÉireannaigh) are an ethnic group who originate in Ireland, an island in northwestern Europe. Ireland has been populated for around 9,000 years (according to archaeological studies, see Prehistoric Ireland), with the Irish people's earliest ancestors recorded having legends of being descended from groups such as the Nemedians, Fomorians, Fir Bolg, Tuatha Dé Danann and the Milesians.
The main groups that interacted with the Irish in the Middle Ages include the Scottish people and the Vikings. Due to this contact, Icelanders are especially noted for having some Irish descent. The Anglo-Norman invasion of the High Middle Ages, the English plantations and the subsequent English rule of the country introduced the Normans and Flemish into Ireland. Welsh, Picts, Bretons, and small parties of Gauls and even Anglo-Saxons are known in Ireland from much earlier times.
There have been many notable Irish people throughout history. The 6th century Irish monk and missionary Columbanus is regarded as one of the "fathers of Europe", followed by Kilian of Würzburg and Vergilius of Salzburg. The scientist Robert Boyle is considered the "father of chemistry". Famous Irish explorers include Brendan the Navigator, Ernest Shackleton, and Tom Crean. By some accounts, the first European child born in North America had Irish descent on both sides; while an Irishman was also the first European to set foot on American soil in Columbus' expedition of 1492.
Large populations of people of Irish ethnicity live in many western countries, particularly in English-speaking countries. Historically, emigration has been caused by politics, famine and economic issues. An estimated 50 to 80 million people make up the Irish diaspora today, which includes Great Britain, the United States, Australia, Canada, Argentina, Chile, Jamaica, Trinidad, South Africa, New Zealand, Mexico, France, Germany and Brazil. The largest number of people of Irish descent live in the United States-about ten times more than in Ireland itself. However, it had been recognised that the estimated numbers of the Irish dispora could be hugely inaccurate, including the majority of ancestral censuses conducted within the United States and Canada, in which it requires self-reported ancestry, often at times completely inaccurate. The majority of people living within immigrated populations (i.e. Australia, United States, Canada etc.) are of mixed ancestry due to decades, at times centuries, of inter-marriage with other immigrants or indigenous populations, hence claiming one specific ancestry is often at times personal preference or perceived ancestry rather than fact. The author Jim Webb also suggests that a large number, he suspects near half of claimed Irish-American ancestry, especially for Protestants, are actually Ulster Scots (Scottish people who populated Northern Ireland, not to be confused with Scottish People)