The History of Ireland began with the first known human settlement in Ireland around 8000 BC, when hunter-gatherers arrived from Britain and continental Europe, probably via a land bridge.

Few archaeological traces remain of this group, but their descendants and later Neolithic arrivals, particularly from the Iberian Peninsula, were responsible for major Neolithic sites such as Newgrange.

Following the arrival of Saint Patrick and other Christian missionaries in the early to mid-5th century, Christianity subsumed the indigenous pagan religion by the year 600. Christianity has played a major role in Ireland's history, culture and internal conflict.
From around 800, more than a century of Viking invasions wreaked havoc upon the monastic culture and on the island's various regional dynasties, yet both of these institutions proved strong enough to survive and assimilate the invaders.

The coming of Anglo-Norman mercenaries under Richard de Clare, 2nd Earl of Pembroke, nicknamed Strongbow, in 1169 marked the beginning of more than 800 years of direct English involvement in Ireland. The English crown did not begin asserting full control of the island until after the English Reformation, when questions over the loyalty of Irish vassals provided the initial impetus for a series of military campaigns between 1534 and 1691. This period was also marked by an official English policy of plantation which led to the arrival of thousands of English and Scottish Protestant settlers. From this period on, sectarian conflict became a recurrent theme in Irish history.

Throughout this period, Ireland regained a form of self-governing status through the Parliament of Ireland, but power was limited to the Anglo-Irish, Anglican minority while the majority Roman Catholic population suffered severe political and economic privations. In 1801, this parliament was abolished and Ireland became an integral part of a new United Kingdom of Great Britain and Ireland under the Act of Union.

In 1922, after the Irish War of Independence, the southern twenty-six counties of Ireland seceded from the United Kingdom (UK) to become the independent Irish Free State — and after 1948, the Republic of Ireland.
The remaining six north eastern counties, known as Northern Ireland, remained part of the UK. The history of Northern Ireland has been dominated by sporadic sectarian conflict between (mainly Catholic) Nationalists and (mainly Protestant) Unionists. This conflict erupted into the Troubles in the late 1960s, until an uneasy peace thirty years later.

Early history: 8000 BC–AD 400

What little is known of pre-Christian Ireland comes from a few references in Roman writings, Irish poetry and myth, and archaeology. The earliest inhabitants of Ireland, people of a mid-Stone Age, or Mesolithic, culture, arrived sometime after 8000 BC, when the climate had become more hospitable following the retreat of the polar icecaps.

About 4000 BC agriculture was introduced from the continent, leading to the establishment of a high Neolithic culture, characterized by the appearance of pottery, polished stone tools, rectangular wooden houses and communal megalithic tombs, some of which are huge stone monuments like the Passage Tombs of Newgrange, Knowth and Dowth, many of them astronomically aligned (most notably, Newgrange).
Four main types of megalithic tomb have been identified: Portal Tombs, Court Tombs, Passage Tombs and Wedge Tombs.

In Leinster and Munster individual adult males were buried in small stone structures, called cists, under earthen mounds and were accompanied by distinctive decorated pottery. This culture apparently prospered, and the island became more densely populated. Towards the end of the Neolithic new types of monuments developed, such as circular embanked enclosures and timber, stone and post and pit circles.
The Bronze Age properly began once copper was alloyed with tin to produce true bronze artifacts, this took place around 2000 BC, when some Ballybeg flat axes and associated metalwork was produced.
The period preceding this, in which Lough Ravel and most Ballybeg axes were produced, and is known as the Copper Age or Chalcolithic, commenced about 2500 BC.

This period also saw the production of elaborate gold and bronze ornaments, weapons and tools. There was a movement away from the construction of communal megalithic tombs to the burial of the dead in small stone cists or simple pits, which could be situated in cemeteries or in circular earth or stone built burial mounds known respectively as barrows and cairns.

As the period progressed inhumation burial gave way to cremation and by the Middle Bronze Age cremations were often placed beneath large burial urns. The Iron Age in Ireland began about 600 BC. By the historic period (AD 431 onwards) the main over-kingdoms of In Tuisceart, Airgialla, Ulaid, Mide, Laigin, Mumhain, Cóiced Ol nEchmacht began to emerge (see Kingdoms of ancient Ireland).
Within these kingdoms a rich culture flourished. The society of these kingdoms was dominated by an upper class, consisting of aristocratic warriors and learned people, possibly including druids. Historians developed the concept from the 17th century onwards that the language spoken by these people could be called the Goidelic languages, a branch of the Celtic languages, and this was explained as a result of invasions of Celts.

However, research during the 20th century indicated otherwise, and in the later years of the century the conclusion drawn was that culture developed gradually and continuously, and that the introduction of Celtic language and elements of Celtic culture was a result of cultural exchange with Celtic groups on southwest continental Europe from the Neolithic to the Bronze Age.
Little archaeological evidence was found for large intrusive groups of Celtic immigrants in Ireland.

The hypothesis that the native Late Bronze Age inhabitants gradually absorbed Celtic influences has since been supported by some recent genetic research.
The Romans referred to Ireland as Hibernia. Ptolemy in AD 100 records Ireland's geography and tribes.
Ireland was never formally a part of the Roman Empire but Roman influence was often projected well beyond formal borders. Tacitus writes that an exiled Irish prince was with Agricola in Britain and would return to seize power in Ireland. Juvenal tells us that Roman "arms had been taken beyond the shores of Ireland".

In recent years, some experts have hypothesized that Roman-sponsored Gaelic forces (or perhaps even Roman regulars) mounted some kind of invasion around 100, but the exact relationship between Rome and the dynasties and peoples of Hibernia remains unclear.

Early Christian Ireland 400–800 

The middle centuries of the first millennium AD marked great changes in Ireland.
Niall Noigiallach (died c.450/455) laid the basis for the Uí Néill dynasty's hegemony over much of western, northern and central Ireland. Politically, the former emphasis on tribal affiliation had been replaced by the 700s by that of patrilineal and dynastic background. Many formerly powerful kingdoms and peoples disappeared.
Irish pirates struck all over the coast of western Britain in the same way that the Vikings would later attack Ireland. Some of these founded entirely new kingdoms in Pictland, Wales and Cornwall.

The Attacotti of south Leinster may even have served in the Roman military in the mid-to-late 300s.
Perhaps it was some of the latter returning home as rich mercenaries, merchants, or slaves stolen from Britain or Gaul, that first brought the Christian faith to Ireland. Some early sources claim that there were missionaries active in southern Ireland long before St. Patrick.

Whatever the route, and there were probably many, this new faith was to have the most profound effect on the Irish. A page from the Book of Kells that opens the Gospel of John.
A page from the Book of Kells that opens the Gospel of John. Tradition maintains that in AD 432, St. Patrick arrived on the island and, in the years that followed, worked to convert the Irish to Christianity. On the other hand, according to Prosper of Aquitaine, a contemporary chronicler, Palladius was sent to Ireland by the Pope in 431 as "first Bishop to the Irish believing in Christ", which demonstrates that there were already Christians living in Ireland.
Palladius seems to have worked purely as Bishop to Irish Christians in the Leinster and Meath kingdoms, while Patrick — who may have arrived as late as 461 — worked first and foremost as a missionary to the Pagan Irish, converting in the more remote kingdoms located in Ulster and Connacht.

Patrick is traditionally credited with preserving the tribal and social patterns of the Irish, codifying their laws and changing only those that conflicted with Christian practices. He is also credited with introducing the Roman alphabet, which enabled Irish monks to preserve parts of the extensive Celtic oral literature.

The historicity of these claims remains the subject of debate. There were Christians in Ireland long before Patrick came, and pagans long after he died. However, it is undoubtedly true that Patrick played a crucial role in transforming Irish society. The druid tradition collapsed, first in the face of the spread of the new faith, and ultimately in the aftermath of famine and plagues due to the climate changes of 535–536.
Irish scholars excelled in the study of Latin learning and Christian theology in the monasteries that flourished shortly thereafter. Missionaries from Ireland to England and Continental Europe spread news of the flowering of learning, and scholars from other nations came to Irish monasteries.

The excellence and isolation of these monasteries helped preserve Latin learning during the Early Middle Ages. The arts of manuscript illumination, metalworking, and sculpture flourished and produced such treasures as the Book of Kells, ornate jewellery, and the many carved stone crosses that dot the island. Sites dating to this period include clochans, ringforts and promontory forts.
The first English involvement in Ireland took place in this period. In 684 AD an English expeditionary force sent by Northumbrian King Ecgfrith invaded Ireland in the summer of that year.

The English forces managed to seize a number of captives and booty, but they apparently did not stay in Ireland for long. The next English involvement in Ireland would take place a little more than half a millennium later in 1169 AD when the Normans invaded the country.

Early medieval era 800–1166

The first recorded Viking raid in Irish history occurred in 795 when Vikings from Norway looted the island of Lambay, located off the Dublin coast. Early Viking raids were generally small in scale and quick.
These early raids interrupted the golden age of Christian Irish culture starting the beginning of two hundred years of intermittent warfare, with waves of Viking raiders plundering monasteries and towns throughout Ireland. Most of the early raiders came from the fjords of western Norway.

By the early 840s, the Vikings began to establish settlements along the Irish coasts and to spend the winter months there.
Vikings founded settlements in Limerick, Waterford, Wexford, Cork, Arklow and most famously, Dublin. Written accounts from this time (early to mid 840s) show that the Vikings were moving further inland to attack (often using rivers such as the Shannon) and then retreating to their coastal headquarters.

In 852, the Vikings Ivar Beinlaus and Olaf the White landed in Dublin Bay and established a fortress, on which the city of Dublin (from the Irish Gaelic An Dubh Linn meaning "the black pool") now stands.
Olaf was the son of a Norwegian king and made himself the king of Dublin.
After several generations a group of mixed Irish and Norse ethnic background arose (the so-called Gall-Gaels, Gall then being the Irish word for "foreigners" — the Norse).

The descendants of Ivar Beinlaus established a long dynasty based in Dublin, and from this base succeeded in briefly dominating large parts of central and eastern Ireland. However, the Vikings never achieved total domination of Ireland, often fighting for and against various Irish kings, such as Flann Sinna, Cerball mac Dúnlainge and Niall Glúndub.

Ultimately they were suborned by King Máel Sechnaill mac Domnaill of Meath at the battle of Tara in 980, though the credit is often erronously given to Brian Boru. Early Ireland had an unusual government. Ireland was divided into many small kingdoms called tuaths.

Each tuath's king was elected by all the free men on its territory. The tuath was thus a body of persons voluntarily united and its territorial dimension was the sum total of the landed properties of its members.
About 80 to 100 tuatha coexisted at any time throughout Ireland. Above the tuaithe were larger provincial kingdoms.

Free State/Republic (1922-present)

The treaty to sever the Union divided the republican movement into anti-Treaty (who wanted to fight on until an Irish Republic was achieved) and pro-Treaty supporters (who accepted the Free State as a first step towards full independence and unity). Between 1922 and 1923 both sides fought the bloody Irish Civil War. The new Irish Free State government defeated the anti-Treaty remnant of the Irish Republican Army.

This division among nationalists still colours Irish politics today, specifically between the two leading Irish political parties, Fianna Fáil and Fine Gael. The new Irish Free State (1922–37) existed against the backdrop of the growth of dictatorships in mainland Europe and a major world economic downturn in 1929.

In contrast with many contemporary European states it remained a democracy. Testament to this came when the losing faction in the Irish civil war, Eamon de Valera's Fianna Fáil, was able to take power peacefully by winning the 1932 general election. Nevertheless, up until the mid 1930s, considerable parts of Irish society saw the Free State through the prism of the civil war, as a repressive, British imposed state. It was only the peaceful change of government in 1932 that signalled the final acceptance of the Free State on their part. In contrast to many other states in the period, the Free State remained financially solvent as a result of low government expenditure. However, unemployment and emigration were high.

The population declined to a low of 2.7 million recorded in the 1961 census. The Roman Catholic Church had a powerful influence over the Irish state for much of its history. The clergy's influence meant that the Irish state had very conservative social policies, banning, for example, divorce, contraception, abortion, pornography as well as encouraging the censoring of many books and films. In addition the Church largely controlled the State's hospitals, schools and remained the largest provider of many other social services. With the partition of Ireland in 1922, 92.6% of the Free State's population were Catholic while 7.4% were Protestant.[7] By the 1960s, the Protestant population had fallen by half.

Although emigration was high among all the population, due to a lack of economic opportunity, the rate of Protestant emigration was disproportionate in this period. Many Protestants left the country in the early 1920s, either because they felt unwelcome in a predominantly Catholic and nationalist state, because they were afraid due to the burning of Protestant homes (particularly of the old landed class) by republicans during the civil war, because they regarded themselves as British and did not wish to live in an independent Irish state, or because of the economic disruption caused by the recent violence.

The Catholic Church had also issued a decree, known as Ne Temere, whereby the children of marriages between Catholics and Protestants had to be brought up as Catholics. From 1945, the emigration rate of Protestants fell and they became less likely to emigrate than Catholics - indicating their integration into the life of the Irish State. In 1937, a new Constitution of Ireland proclaimed the state of Éire (or Ireland). The state remained neutral throughout World War II (see Irish neutrality) and this saved it from much of the horrors of the war, although tens of thousands volunteered to serve in the British forces.

Ireland was also hit badly by rationing of food, and coal in particular (peat production became a priority during this time). Though nominally neutral, recent studies have suggested a far greater level of involvement by the South with the Allies than was realised, with D Day's date set on the basis of secret weather information on Atlantic storms supplied by Éire. For more detail on 1939–45, see main article The Emergency. In 1949 the state was formally declared the Republic of Ireland and it left the British Commonwealth. In the 1960s, Ireland underwent a major economic change under reforming Taoiseach (prime minister) Seán Lemass and radical senior civil servant T.K. Whitaker, who produced a series of economic plans.

Free second-level education was introduced by Donnchadh O'Malley as Minister for Education in 1968. From the early 1960s, the Republic sought admission to the European Economic Community but, because 90% of the export economy still depended on the United Kingdom market, it could not do so until the UK did, in 1973.

Global economic problems in the 1970s, augmented by a set of misjudged economic policies followed by governments, including that of Taoiseach Jack Lynch, caused the Irish economy to stagnate. The Troubles in Northern Ireland discouraged foreign investment. Devaluation was enabled when the Irish Pound, or Punt, was established in as a truly separate currency in 1979, breaking the link with the UK's sterling. However, economic reforms in the late 1980s, the end of the Troubles, helped by investment from the European Community, led to the emergence of one of the world's highest economic growth rates, with mass immigration (particularly of people from Asia and Eastern Europe) as a feature of the late 1990s.

This period came to be known as the Celtic Tiger and was focused on as a model for economic development in the former Eastern Bloc states, which entered the European Union in the early 2000s. Property values had risen by a factor of between four and ten between 1993 and 2006, in part fuelling the boom. Irish society also adopted relatively liberal social policies during this period.

Divorce was legalised, homosexuality decriminalised, while abortion in limited cases was allowed by the Irish Supreme Court in the X Case legal judgement. Major scandals in the Roman Catholic Church, both sexual and financial, coincided with a widespread decline in religious practice, with weekly attendance at Roman Catholic Mass halving in twenty years.

A series of tribunals set up from the 1990s have investigated alleged malpractices by politicians, the Catholic clergy, judges, hospitals and the Gardaí (police).

Northern Ireland

"A Protestant State" (1921-1971)

From 1921 to 1971, Northern Ireland was governed by the Ulster Unionist Party government, based at Stormont in East Belfast. The founding Prime Minister, James Craig, proudly declared that it would be "a Protestant State for a Protestant People" (in contrast to the anticipated "Papist" state to the south).

Discrimination against the minority nationalist community in jobs and housing, and their total exclusion from political power due to the majoritarian electoral system, led to the emergence of the Northern Ireland Civil Rights Association in the late 1960s, inspired by Martin Luther King's civil rights movement in the United States of America. A violent counter-reaction from right-wing unionists and the Royal Ulster Constabulary (RUC) led to civil disorder, notably the Battle of the Bogside and the Northern Ireland riots of August 1969.

To restore order, British troops were deployed to the streets of Northern Ireland at this time. Tensions came to a head with the events of Bloody Sunday and Bloody Friday, and the worst years (early 1970s) of what became known as the Troubles resulted. The Stormont parliament was prorogued in 1971 and abolished in 1972. Paramilitary private armies such as the Provisional Irish Republican Army, the Official IRA, the Irish National Liberation Army, the Ulster Defence Association and the Ulster Volunteer Force fought each other and the British army and the (largely Unionist) RUC, resulting in the deaths of well over three thousand men, women and children, civilians and military. Most of the violence took place in Northern Ireland, but some also spread to England and across the Irish border.

Direct rule (1971-1998)

For the next 27 years, Northern Ireland was under "direct rule" with a Secretary of State for Northern Ireland in the British Cabinet responsible for the departments of the Northern Ireland executive/government. Principal acts were passed by the Parliament of the United Kingdom in the same way as for much of the rest of the UK, but many smaller measures were dealt with by Order in Council with minimal parliamentary scrutiny.

Throughout this time the aim was to restore devolution, but three attempts - the power-sharing executive established by the Northern Ireland Constitution Act and the Sunningdale Agreement, the 1975 Northern Ireland Constitutional Convention and Jim Prior's 1982 assembly - all failed to either reach consensus or operate in the longer term.

During the 1970s British policy concentrated on defeating the Provisional Irish Republican Army (IRA) by military means including the policy of Ulsterisation (requiring the RUC and British Army reserve Ulster Defence Regiment to be at the forefront of combating the IRA). Although IRA violence decreased it was obvious that no military victory was on hand in either the short or medium terms. Even Catholics that generally rejected the IRA were unwilling to offer support to a state that seemed to remain mired in sectarian discrimination, and the Unionists plainly were not interested in Catholic participation in running the state in any case.

In the 1980s the IRA attempted to secure a decisive military victory based on massive arms shipments from Libya.
When this failed - probably because of MI5's penetration of the IRA's senior commands - senior republican figures began to look to broaden the struggle from purely military means. In time this began a move towards military cessation. In 1986 the British and Irish governments signed the Anglo Irish Agreement signalling a formal partnership in seeking a political solution. Socially and economically Northern Ireland suffered the worst levels of unemployment in the UK and although high levels of public spending ensured a slow modernisation of public services and moves towards equality, progress was slow in the 1970s and 1980s, only in the 1990s when progress towards peace became tangible, did the economic situation brighten. By then, too, the demographics of Northern Ireland had undergone significant change, and more than 40% of the population are Catholics.

Devolution and direct rule (1998-present)

More recently, the Belfast Agreement ("Good Friday Agreement") of April 10, 1998 brought a degree of power sharing to Northern Ireland, giving both unionists and nationalists control of limited areas of government. However, both the power-sharing Executive and the elected Assembly have been suspended since October 2002 following a breakdown in trust between the political parties.

Efforts to resolve outstanding issues, including "decommissioning" of paramilitary weapons, policing reform and the removal of British army bases are continuing.
Recent elections have not helped towards compromise, with the moderate Ulster Unionist and (nationalist) Social Democrat and Labour parties being substantially displaced by the hard-line Democratic Unionist and (nationalist) Sinn Féin parties.

On July 28, 2005, the Provisional IRA announced the end of its armed campaign and on September 25, 2005 international weapons inspectors supervised the full disarmament of the PIRA.