Holy Cross Abbey (Mainistir na Croise Naofa) is a restored Cistercian monastery situated on the River Suir. It takes its name from a relic of the True Cross or Holy rood. The fragment of that Holy Rood was brought to Ireland by the Plantagenet Queen, Isabella of Angoulême around 1233. She was the widow of King John and bestowed the relic on the original Cistercian Monastery in Thurles, which she then rebuilt, and which was thenceforth thereby named Holy Cross Abbey. With time, Holy Cross Abbey and the sacred relic of the True Cross became a place of great medieval pilgrimage, and with the Reformation, also a rallying-point for the dispossessed and victims of religious persecution.
The Holy Rood relic was last exposed for public veneration in 1632, and following the Cromwellian war, Holy Cross Abbey fell into ruins. Local people used the roofless ruins as a burial place after 1740. In 1969, Holy Cross Abbey was restored as a place of Catholic worship. The Sacristan of St. Peter's Basilica in the Vatican provided an authenticated relic of the Holy Cross, and the emblem of the Jerusalem Cross, or Crusader Cross, has been restored for the Abbey.