The Monastery of Saint Thaddeus (Armenian: Սուրբ Թադէոսի վանք, Surb Tadeosi vank; Persian: کلیسای تادئوس مقدس, Kelisā-ye Tādeus moghadas) is an ancient Armenian monastery in the mountainous area of West Azerbaijan Province, Iran. It is believed to be one of the oldest church buildings in the world.

Also known as Kara Kilise (the "Black Church") (Persian: قره‌ کلیسا, Qare Kelisā), it is located about 20 kilometers from the town of Chaldiran. The monastery and its distinctive Armenian conical roofs are visible from long distances.

The Monastery is site of the Pilgrimage of St. Thaddeus which in 2020 was added by UNESCO to its list of Intangible Cultural Heritage.