The name Waterford us derived Old Norse Veðrafjǫrðr, meaning "ram (wether) fjord".

Mesolithic people are known to have been in this area of Ireland some 8,000  to 10,000 years ago. The fine harbors, coastal coves and the navigable waters of the Suir and the Blackwater rivers attracted them.

Between 5,000-4,000 years ago sophisticated tribes who were engaged in agriculture took root in Ireland. During their tenure they built the great megalithic tombs, sixteen of which lie in Waterford.

St. Declan founded his monastery at Ardmore in 416 and was preaching the Christian message before the arrival of St. Patrick. Lismore was a renowned educational establishment which attracted influential figures from all over Europe to study there.

County Waterford is colloquially known as "The Déise", pronounced "day-sha" (Irish: An Déise). Sometime between the 4th and 8th centuries, a tribe of native Gaelic people called the Déise were driven from southern county Meath/north Kildare, conquering and settling the area now known as Waterford. The ancient principality of the Déise is roughly coterminous with the Roman Catholic Diocese of Waterford and Lismore .

Waterford is Ireland's oldest city and was founded by the Vikings in the 9th century. The earliest Viking settlement in the Waterford area was at the early to mid-ninth century site at Woodstown about three miles from the present city.

It was taken over by the Anglo-Norman invaders of the 12th century and was one of the most important Old English centers in medieval Ireland. In 1171, Henry II of England became the first English king to set foot in an Irish city, by landing with a large fleet at Waterford.

In 1649 Waterford became the only Irish town to successfully resist Cromwell. After the Battle of the Boyne in 1690, both King James II and King William of Orange came by Waterford; James on his retreat  to France and the victorious ”King Billy” returning to England.

In 1783 George and William Penrose founded a glass factory. So began Waterford Crystal.

Thomas Francis Meagher, an Irish nationalist from Waterford and a leader of the 1848 Rebellion brought a tricolour back from France and it was first flown from a building on the Mall in Waterford in 1848.

After the evacuation of British troops from Waterford city at the end of the Irish War of Independence the military and police barracks were occupied by the Waterford Flying Column. These troops opposed the Anglo-Irish Treaty of 1922 and therefore took the Republican side when the Irish Civil War commenced