St Mary's Cathedral is a cathedral church of the Diocese of Tuam, Limerick and Killaloe in the Church of Ireland. It is located in Tuam, County Galway, in Ireland. From the 12th century until 1839, both before and after the Reformation, it was the seat of the former Archdiocese of Tuam. Most of the present structure dates from the 1870s, but parts of earlier 12th- and 14th-century structures survive within.