- Man arrives in Ireland across a landbridge from Britain.
- New settlers of uncertain origin arrive.
- The New Stone Age begins and sites like Newgrange (c. 2500 BC) are constructed.
- Farming lifestyle leads to woods being cut down.
- "Beaker People" arrive in Ireland.
- Bronze Age begins.
- Metalworking becomes an art, especially gold ornaments are created (some impressive hoards are on display in the National Museum of Ireland).
- Celtic invaders reach Ireland.
- Concept of High King (ard ri) becomes important.
- Royal Seats like the Hill of Tara established.
- First massive arrival of Celtic peoples in Ireland.
- Agricola, Britain's Roman governor, contemplates invasion of Ireland; this is never attempted, but trade contacts exist.
- Ptolomy writes about Ireland in his geographical works.
- Irish invade (mainly) the northern part of Britain, they are known as Scots.
- Palladius is sent from Rome to Ireland as a bishop.
- Patrick starts his Irish mission.
- His fast of 40 days on Croagh Patrick is legendary.
- Patrick founds church at Armagh.
- Irish monasticism develops and grows.
- Irish monk Columba establishes his own monastery on Iona (Hebrides, Scotland).
- Irish "Golden Age", illuminated manuscripts like the "Book of Kells" (on display in Trinity College)and metalware like the "Ardagh Chalice" (today in the National Museum Kildare Street) are created.
- Monasticism and learning flowers.
