Saint Gregory of Nyssa was a church and monastery located in the Pontic city of Trebizond (Trk: Trabzon). It's believed the monastery was built by Eudokia Comnene Palaiologina who was the wife of John II, Emperor of Trebizond (1280-1297). The temple had beautiful inscriptions on its walls depicting the Empress and Emperor themselves. After 1665, following the conversion of St. Philip into a mosque, St. Gregory became the cathedral of the city of Trebizond.

In 1850, George Finlay described the church by saying...'The metropolitan church is a small building within the same court as the episcopal residence.' He also mentioned that the church had north and south porches.

Before 1863 St. Gregory was a medieval monastery. The Metropolitan Constantius of Trebizond (1830-79) was responsible for rebuilding many medieval monuments during his long reign. In 1863, he set out on his most ambitious project, that of rebuilding St.Gregory of Nyssa. He did this by building a large church which comprised 3 Pontic apses, a belfry, and a deca-hexagonal drum as its dome. The church was dynamited in 1930 to make way for the City Club.

The church is dedicated to St.Gregory of Nyssa (c. 330-395), a Christian bishop and saint. Nyssa (current day Nevşehir) is a city located in Cappadocia.