Hagia Eirene (also known as Hagia Irene or Saint Irene) is an early Eastern Orthodox church located in Istanbul, Turkey. It is one of the few churches in Istanbul that has been in continuous use as a place of worship since it was built in the 4th century. The church is located within the grounds of the Topkapı Palace, and is now used as a museum. It is considered one of the oldest surviving churches in Istanbul, and is known for its beautiful architectural features, including its dome and marble columns. The church is named after Irene of Athens, a Christian saint who was martyred in the 4th century.