The Rev Pat Storey, 53, a married mother of two, was appointed by the Church of Ireland to be Bishop of Meath and Kildare, in the Republic.
She was consecrated in a ceremony at Christ Church Cathedral in Dublin.
The Church, whose territory also includes Northern Ireland, decided to appoint women as priests and bishops in 1990 but until now had not appointed one.
Mrs Storey’s consecration comes just 10 days after the Church of England’s General Synod voted overwhelmingly in favour of women bishops, ending a 13-year battle over the issue.
The bishop grew up in Belfast and studied French and English at Trinity College in Dublin. Bishop Storey and her husband have two adult children Luke, 22, and Carolyn, 25, and son-in-law Peter.
She only entered the clergy in her mid thirties after working as a receptionist in a doctor's surgery and for Weight Watchers.