Hagia Irene or Hagia Eirene, sometimes known also as Saint Irene, is an Eastern Orthodox church located in the outer courtyard of Topkapı Palace in Istanbul. It is the oldest known church in the city and one of the only Byzantine churches in Istanbul that was never converted into a mosque, alongside the Church of Saint Mary of the Mongols, as it was used as an arsenal for storing weapons until the 19th century. The Hagia Irene today operates as a museum and concert hall.