St. Mary's Church, Castlemartin, located in the broad Kilcullen area of County Kildare, Ireland, is the first medieval church in Ireland to have been restored to full working order. The small stone Roman Catholic church, with accompanying burial ground, lies within Castlemartin Estate, which belongs to media magnate Tony O'Reilly; O'Reilly paid for the restoration in 1979–1980, after which the church was reconsecrated in August 1981 by Archbishop Dermot Ryan. There has been a church on this site for over 800 years.