Ireland is first inhabited by humans around 6000 BCE. Celts from continental Europe begin to arrive around 600 BCE. Over time the Celt immigrants begin to identify themselves as Gaels.
Christianity (Roman Catholicism) is introduced to the island in the 5th Century CE by Saint Patrick. Three hundred years later the Vikings appear, at first conducting raids but later establishing permanent settlements. Though their influence is almost completely neutralised following the Battle of Clontarf on Good Friday 23 April 1014, the Vikings remain a presence up to and beyond the invasion of the island by the English Normans in 1169.
By 1250 the English Normans control three quarters of the island. However, their hold is brittle. A Gaelic resurgence pushes them back, loosening the English grip until the island is reconquered and Anglicised during the reign of the Tudor monarchs in the 16th Century.
Protestants from Scotland and England begin to settle in the north of the island and around Dublin early in the 17th Century. They eventually constitute about 25% of the population. Under the "Plantation" system over 80% of the island's productive land is taken from the Irish and handed to the English and Scottish settlers. The Catholic Irish natives become their landless, disenfranchised tenants.
The Catholic Irish are further marginalised by the introduction of a series of Penal Laws during the so-called Protestant Ascendancy of the 18th Century.
The Penal Laws are progressively repealed from the 1770s onward. In 1793 Catholics are given the right to vote, but with a restricted franchise. They are still prohibited from serving in parliament.
In 1800, following widespread, mainly Protestant-led unrest and a number of abortive uprisings, the Irish Parliament passes the Act of Union, making Ireland part of the United Kingdom and ending a short-lived period of semi-autonomous government.
In 1829, after the Catholic activist Daniel O'Connell exploits a loophole in the law and wins a by-election, Catholics are given the right to serve in parliament. Most of the remaining Penal Laws are repealed. However, calls for Irish independence are rejected.
Meanwhile, a severe economic depression inside Ireland is exacerbated when the repeated failure of the potato crop due to a fungal infection ushers in the Great Famine of 1845-1849 (also known as the Great Hunger). Potatoes are the staple food of the country's poor. The famine sees hundreds of thousands perish or flee.
Before the Great Famine the population of Ireland is 8.5 million. After it is 6.5 million. Half of the two million difference is attributable to deaths due to starvation, deprivation and disease. The other half is a result of mass emigration to foreign lands, principally the United States.
While the poor starve, large quantities of wheat, oats, barley and other crops are exported from the country. The government does little to intervene or assist. By the time the famine finally ends, resentment towards the English has reached new heights.
The Irish Republican Brotherhood is formed in 1858. The Brotherhood is an underground organisation dedicated to launching an armed rebellion against the English at an opportune moment.
At the same time, the Home Rule Movement works to obtain Irish independence through legal means. Under the leadership of Charles Stewart Parnell, the movement forces the English Parliament to introduce two Home Rule bills, in 1886 and 1893, both of which are defeated.
In 1905 Sinn Féin (Ourselves Alone) is formed by Dublin journalist Arthur Griffith.