The Church of the Seat of Mary (Ecclesia Kathismatis, from Greek Kathisma "Seat") was a 5th-century Byzantine church in the Holy Land, located between Jerusalem and Bethlehem, near Mar Elias Monastery. The church was built when Marian devotion first rose to great importance, following the Council of Ephesus of 431. It is the first church known to have been dedicated to the Theotokos in the entire Byzantine Empire.
Its remains were discovered accidentally during construction work of Highway 60 in 1992. The course of the highway was shifted to avoid damage to the site, so that the ruins are now just off the road, at the municipal border between Jerusalem and Bethlehem. The site was excavated in 1997, revealing a large church, originally built in the 5th century and restored in the 6th. It was turned into a mosque in the 8th century, and destroyed shortly after. The building had an octagonal floor plan measuring 43 m x 52 m, comparable to that of the 4th-century Nativity Grotto in Bethlehem and other Byzantine churches, imitated in the construction of the Dome of the Rock in the late 7th century. Most of the rooms of the church were paved in coloured mosaics of floral and geometric designs, some of them added in the 8th century.
The church is mentioned in a 6th-century Life of Theodosius the Cenobiarch. According to this text, both the church and the monastery of Kathisma were built by a wealthy widow called Ikelia (Iqilia, Hicelia) during the reign of bishop Juvenal of Jerusalem (r. 450–458). It was built on the supposed resting place of Mary on the road to Bethlehem mentioned in the Proto-Gospel of James. Theodosius is said to have lived in the monastery as a young monk.