Celts, Christianization & Vikings (until 1169)

Ireland's earliest known inhabitants left monumental traces: Newgrange (circa 3200 BC) is older than the pyramids and proves a highly developed Stone Age culture with astronomical knowledge. Around 500 BC, the Celts reached the island and shaped Ireland forever: their language (Gaeilge lives on today), their art (Celtic knots, spirals, crosses), their mythology (Cú Chulainn, the Tuatha Dé Danann, the Sídhe fairy hills), and their social order of kings, druids, and bards.

In the 5th century, Saint Patrick (a Romano-British slave who was kidnapped to Ireland, escaped, and returned as a missionary) came and Christianized the island. The fusion of Celtic culture and Christianity created something unique: Irish monks became the preservers of European civilization during the Dark Ages. In monasteries like Clonmacnoise, Glendalough, and Skellig Michael, they copied ancient texts and created masterpieces like the Book of Kells.

From 795, the Vikings arrived — initially as raiders, then as settlers who founded cities: Dublin (Dubh Linn, "black pool"), Waterford, Cork, Limerick, and Wexford are all Viking foundations. The Battle of Clontarf (1014), where High King Brian Boru defeated the Vikings (but fell himself), ended their dominance.