Born in Country Meath in 1629, Oliver studied for the priesthood in Rome and was ordained there in 1654. After some years of teaching and service to the poor of Rome he was appointed Archbishop of Armagh in Ireland.
Archbishop Plunkett was arrested and imprisoned in Dublin Castle in 1679, but his trial was moved to London. After deliberating for 15 minutes, a jury found him guilty of fomenting revolt. He was hanged, drawn, and quartered in July 1681.
Pope Paul VI canonized Oliver Plunkett in 1975.