Koca Mustafa Pasha Mosque is a former Eastern Orthodox church converted into a mosque by the Ottomans, located in Istanbul, Turkey. The church, as the adjoining monastery, was dedicated to Saint Andrew of Crete, and was named Saint Andrew in Krisei or by-the-Judgment. Although heavily transformed during both the Byzantine and the Ottoman eras, it is one of the few extant churches in Istanbul whose foundation goes back to the sixth century.