Wexford takes its name from the principal town, Wexford, named 'Waesfjord' by the Vikings – meaning 'inlet (fjord) of the mud-flats' in the Old Norse language.

In pre-Norman times it was part of the Kingdom of Uí Cheinnselaig, with its capital at Ferns.

The County was formed in 1210 by King John during a visit to Ireland.

On Ptolemy's mid-2nd century 'Map' of Ireland Carnsore point appears as the Sacred Cape, the river Barrow as the Birgos (or Birgus), most of the area of County Wexford is shown as inhabited by a tribe called the Brigantes, and a tribe called the Coriondi (or Koriondoi) are shown as occupying north County Wexford

Early Irish tribes, forming the Kingdom of Uí Cheinnselaig included the Beanntraige, Uí Dego, Sil mBrain, Uí Bairrche, Fotharta Mara, and the Síl Maíluidir.

The county was one of the earliest areas of Ireland to be Christianized.

The first recorded raid by the Vikings in County Wexford

occurred in 819, when Begerin and Camhain's Oak Island  in Wexford Harbour were plundered. In 835 Ferns was plundered and in 839 it was burned by them.

Wexford was the site of an invasion by Normans in 1169 at the behest of Diarmuid Mac Murrough, King of Uí Cheinnsealaig and King of Leinster (Laigin), which led to the subsequent colonization of the country by the Anglo-Normans.

The native Irish began to regain some of their former territories in the 14th century. One of the main leaders of the revival was Art MacMurrough Kavanagh, who was King of Leinster

On October 12 1649 when Cromwellian forces broke into Wexford they slaughtered 300 women who had sought refuge under an ancient cross in the town square.

In 1798 County Wexford was the area that had the most successful rebellion. The significant rebel victories were in Oulart, Enniscorthy, and Wexford town. At the Battle of Vinegar Hill, the Rebels were defeated.

On Thursday, 27 April 1916, Enniscorthy town was taken over by about 600 armed rebels. The government responded by sending a force of more than 1,000 men to retake Enniscorthy. On Monday, 1 May 1916, the Enniscorthy rebels surrendered unconditionally.

Michael O'Hanrahan of New Ross, who played a prominent role in the Easter Rising at Dublin, was executed 4 May 1916.

The Kennedy political dynasty can trace their Irish roots to Dunganstown in Wexford. Patrick Kennedy, the great-grandfather of John, Bobby and Teddy, left Ireland in 1848 to escape the grinding poverty and famine. His wife Bridget Murphy also came from Wexford.