Following the Bronze and Copper ages, Ireland began to develop what would become its five famous kingdoms: Ulaid (Ulster), Cóiced Ol nEchmacht (Connacht), Mhumhain (Munster), Laighin (Leinster), and the central kingdom of Míde (Meath), which is where the High King presided at Tara. Each of the kingdoms contained many tuatha, or smaller kingdoms within kingdoms. Druid life also began to thrive in this period, with many Druid settlements forming by 600 B.C.

Roman influence in Ireland came about by 100 C.E., when Ptolemy first documented the island and its peoples. Unlike Britain, Ireland was never fully Romanized; the historical record suggests the Irish and the Romans may have collaborated more as peers than they tried to conquer each other.

Christianity arrived in Ireland by the 5th Century C.E., particularly with the arrival of Patrick and Palladius, traditionally believed to have taken place around 432 C.E. The Irish adopted many aspects of the Christian lifestyle while still retaining many of their roots, leading to what is known as classical Celtic Christianity, not to be confused with the vastly different Celtic Christianity of today. The Irish adopted the Roman alphabet, allowing monks to write some of the most beautiful manuscripts known today, including the Book of Kells. The thriving monastery movement continued through the Early Medieval Period.

Before the English ever entered Ireland, there were the Viking invasions, which took place between the late 8th and early 11th centuries. The Vikings created many of Ireland's most famous settlements, including Dublin, Cork, Waterford, Limerick, and Wexford. Alliances were created between the Vikings and the local tuatha, leading to bloody conflicts later on between kingdoms.

The Normans arrived in Ireland in the 12th Century, at a time when local infighting had led to Ireland having an unstable political climate. King Henry II arrived at Waterford in 1171, marking the start of the English presence on Irish soil which continues to this day. The Normans remained strong in Ireland until the mid-13th Century, at which point the Irish led a resurgance to reclaim their land. The Black Plague's arrival killed off many of the Norman and English settlers.

England was not a strong force in Ireland again until the Reformation. The Tudors led another campaign for Ireland, this time much more successful than previous attempts. Civil wars and the Penal Laws led to much bloodshed among the population. Irish Catholics began to take up arms against the British Protestants now in Ireland. Thousands of Irish were forced into the west of Ireland to make room for more British settlers.

English colonialism was firmly entrenched by the late 17th Century. Although the Great Potato Famine of the mid-1700s killed hundreds of thousands of the Irish, the population continued to grow and the period was considered relatively peaceful. It was not until the late 18th Century that a strong nationalist movement began to spring up among the Irish Catholics who wanted the British Protestants off the island, particularly their government. After several attempts at overthrowal, the Union with Great Britain took place in 1801, which would last until 1922. The Irish Catholic population became more aggressive, eventually recruiting many Protestants to the side of the nationalists. Parliament attempted to institute Home Rule multiple times, always failing for various reasons.

The Easter Rising (or Easter Rebellion) of 1916 was the major driving force behind the War of Independence, which concluded in 1921 with the partition of Ireland, creating the Irish Republic comprised of 26 counties and Northern Ireland, comprised of the remaining six. The political and religious conflicts – often the same thing, often different – have raged since, lessening only in more recent years, particularly due to the Good Friday Agreement and the disarmament of the most widespread paramilitaries, including the Irish Republican Army and the Ulster Volunteer Force. Modern Ireland is best known for its thriving economy, which is considered the strongest in Europe, as well as its many contributions to the arts.