The pre-Christian era in Ireland is known chiefly through legend, although there is archaeological evidence of habitation during the Stone and Bronze ages. In about the 4th century BC , the tall, redhaired Celts from Gaul or Galicia arrived, bringing with them the Iron Age. They subdued the Picts in the north and the Érainn tribe in the south, then settled down to establish a Gaelic civilization, absorbing many of the traditions of the previous inhabitants. By the 3rd century AD , the Gaels had established five permanent kingdoms—Ulster, Connacht, Leinster, Meath (North Leinster), and Munster—with a high king, whose title was often little more than honorary, at Tara. After St. Patrick's arrival in AD
432, Christian Ireland rapidly became a center of Latin and Gaelic learning. Irish monasteries drew not only the pious but also the intellectuals of the day, and sent out missionaries to many parts of Europe.
Toward the end of the 8th century, the Vikings began their invasions, destroying monasteries and wreaking havoc on the land, but also intermarrying, adopting Irish customs, and establishing coastal settlements from which have grown Ireland's chief cities. Viking power was finally broken at the Battle of Clontarf in 1014. About 150 years later, the Anglo-Norman invasions began. Gradually, the invaders gained control of the whole country. Many of them intermarried, adopted the Irish language, customs, and traditions, and became more Irish than the Gaels. But the political attachment to the English crown instituted by the Norman invasion caused almost 800 years of strife, as successive English monarchs sought to subdue Gaels and Norman-Irish alike. Wholesale confiscations of land and large plantations of English colonists began under Mary I (Mary Tudor) and continued under Elizabeth I, Cromwell, and William III. Treatment of the Irish reached a brutal climax in the 18th century with the Penal Laws, which deprived Catholics and Dissenters (the majority of the population) of all legal rights.
By the end of the 18th century, many of the English colonists had come to regard themselves as Irish and, like the English colonists in America, resented the domination of London and their own lack of power to rule themselves. In 1783, they forced the establishment of an independent Irish parliament, but it was abolished by the Act of Union (1800), which gave Ireland direct representation in Westminster. Catholic emancipation was finally achieved in 1829 through the efforts of Daniel O'Connell, but the great famine of the 1840s, when millions died or emigrated for lack of potatoes while landlords continued to export other crops to England, emphasized the tragic condition of the Irish peasant and the great need for land reform.
A series of uprisings and the growth of various movements aimed at home rule or outright independence led gradually to many reforms, but the desire for complete independence continued to grow. After the bloodshed and political maneuvers that followed the Easter Uprising of 1916 and the proclamation of an Irish Republic by Irish members of Parliament in 1919, the Anglo-Irish Treaty was signed in 1921, establishing an Irish Free State with dominion status in the British Commonwealth. Violent opposition to dominion status and to a separate government in Protestant-dominated Northern Ireland precipitated a civil war lasting almost a year. The Free State was officially proclaimed and a new constitution adopted in 1922, but sentiment in favor of a reunified Irish Republic remained strong, represented at its extreme by the terrorist activities of the Irish Republican Army (IRA). Powerful at first, the IRA lost much of its popularity after Éamon de Valera, a disillusioned supporter, took over the government in 1932. During the civil violence that disrupted Northern Ireland from the late 1960s on, the Irish government attempted to curb the "provisional wing" of the IRA, a terrorist organization that used Ireland as a base for attacks in the north. Beginning in 1976, the government assumed emergency powers to cope with IRA activities, but the terrorist acts continued, most notably the assassination on 27 August 1979 of the British Earl Mountbatten. The Irish government continues to favor union with Northern Ireland, but only by peaceful means. In November 1985, with the aim of promoting peace in Northern Ireland, Ireland and the United Kingdom ratified a treaty enabling Ireland to play a role in various aspects of Northern Ireland's affairs.
The years since the proclamation of the Irish Free State have also witnessed important changes in governmental structure and international relations. In 1937, under a new constitution, the governor-general was replaced by an elected president, and the name of the country was officially changed to Ireland (Éire in Irish). In 1948, Ireland voted itself out of the Commonwealth of Nations, and on 18 April 1949, it declared itself a republic. Ireland was admitted to the UN in 1955 and became a member of the EC in 1973.
Mary Robinson, an international lawyer, activist, and Catholic, who was elected president in November 1990, became the first woman to hold that office. In 1974, while serving in the Irish legislature, she shocked her fellow countrypeople by calling for legal sale of contraceptives. Her victory came at a period in Irish history dominated by controversy over the major issues of the first half of the 1990s: unemployment, women's rights, abortion, divorce, and homosexuality. Robinson promoted legislation that enabled women to serve on juries and gave 18-year-olds the right to vote. In the latter half of the 1990s, the economic situation greatly improved and Ireland recorded growth rates of 7% between 1996–2000. Unemployment fell from 16% in 1993 to 5% in 2000. Due to the global economic downturn that began in 2001, however, even Ireland's booming economy slowed; GDP growth in Ireland was forecast for 3% in 2003.
In 1997, Mary McAleese, who lives in Northern Ireland, became the first British subject to be elected president of the Irish Republic. Her term expires in 2004.
On 10 April 1998 the Irish Republic jointly signed a peace agreement with the United Kingdom to resolve the Northern Ireland crisis. Ireland pledged to amend articles 2 and 3 of the Irish Constitution, which lay claim to the territory of the North, in return for the United Kingdom promising to amend the Government of Ireland Act. On 22 May 1998, 94.4% of the electorate voted in a referendum to drop Ireland's claim to Northern Ireland. A year after the agreement, several key provisions of the Good Friday Agreement had been implemented. The peace process has since then witnessed long moments of gloom in spite of the ongoing involvements of the British and Irish prime ministers to resolve the situation in Northern Ireland. One of the largest obstacles was the disarmament of the IRA and the reservations on the part of the Ulster Unionists to share power with Sinn Feìn, the political arm of the IRA. Finally, in May 2000, the IRA proposed that outside observers be shown the contents of arms dumps and reinspect them at regular intervals to ensure that weaponry had not been removed and was back in circulation. The Ulster Unionists agreed to power-sharing arrangements and to endorse devolution of Northern Ireland. Decommissioning of the IRA did not progress in early 2001, however, and David Trimble, the first minister of the power-sharing government, resigned in July 2001. Sinn Feìn's offices at Stormont, the Northern Ireland Assembly, were raided by the police in October 2002, due to spying allegations. On 14 October 2002, devolution was suspended and direct rule from London returned to Northern Ireland. Elections planned for the assembly in May 2003 were indefinitely postponed by British Prime Minister Tony Blair, due to a lack of evidence of peaceful intentions on the part of the IRA.
In March 2002, Irish voters rejected a referendum proposal that would further restrict abortion laws. The vote was 50.4% against the proposal and 49.6% in favor. The vote was a setback to Prime Minister Bertie Ahern. However, Ahern's Fianna Fáil party overwhelmingly defeated the opposition Fine Gael party in the May 2002 elections. Ireland, unlike the UK, joined the European economic and monetary union in 1999 without problem, and adopted the euro as its currency. However, Irish voters in June 2001 rejected the Treaty of Nice, which allows for the enlargement of the EU. The other 14 members of the EU all approved the treaty by parliamentary vote, but Ireland's adoption required amending the constitution, which stipulated a popular vote. Voter turnout was low (34.8%), and when the treaty was put to Irish voters once again in October 2002, the government conducted a massive education campaign to bring voters to the polls. This time, voter turnout was 48.5%, and 63% of voters in the October referendum approved the Nice Treaty. Ten new EU candidate countries are due to join the body on 1 May 2004.