The Monastery of Saint Thaddeus is an ancient Armenian monastery located in the mountainous region of northwestern Iran, near the border with Azerbaijan and Turkey. The monastery is believed to have been founded in the 1st century AD by the Apostle Thaddeus, one of the twelve apostles of Jesus.

The monastery complex includes several buildings and structures, including the main church, known as the St. Thaddeus Church or the Qara Kelisa (Black Church), a chapel, a bell tower, and several rooms for monks and pilgrims. The St. Thaddeus Church is considered to be one of the oldest surviving Christian churches in the world and is a UNESCO World Heritage Site.

The monastery has undergone several renovations and reconstructions over the centuries, with the current structures dating back to the 14th century. The architecture of the monastery is characterized by its blend of Armenian and Persian styles, with intricate carvings, tile work, and frescoes decorating the interior and exterior of the buildings.

The Monastery of Saint Thaddeus is an important pilgrimage site for Armenian Christians, with thousands of pilgrims visiting the site each year to pay homage to the Apostle Thaddeus and to seek blessings and healing. The monastery is also a popular tourist destination, attracting visitors from around the world who are interested in history, architecture, and religion.