San Gregorio Nazianzeno, Church building in Campo Marzio, Rome, Italy

San Gregorio Nazianzeno is a church in vicolo Valdina, in the Campo Marzio district of Rome. Its brick bell tower and the remains of an apse fresco showing Christ between Saints Gregory of Nazianzus and John Chrysostom date from the 12th century. Restoration between 1977 and 1987 brought to light a room identified as the only surviving part of the original oratory.

San Gregorio Nazianzeno is already named in the biography of Pope Leo III (795–816), which records a silver basket made for the oratory "in campo Martis". The brick bell tower and the remains of an apse fresco of Christ between Saints Gregory Nazianzenus and John Chrysostom date to the 12th century. After 1870 the church was deconsecrated and the adjoining monastery turned into archives; the Chamber of Deputies bought the complex and restored the church between 1977 and 1987, when a room identified as the only surviving part of the original oratory came to light.

The church is named after Gregory of Nazianzus, a 4th-century theologian; the 12th-century apse fresco shows Christ between him and John Chrysostom. The adjoining monastery of Santa Maria in Campo Marzio took its name from the nearby church of Santa Maria della Concezione in Campo Marzio. Since 1987 the restored church has served as the chapel of the Chamber of Deputies.

The church stands in vicolo Valdina, a narrow lane in the Campo Marzio rione, a short walk from Piazza Montecitorio. Since 1977-1987 restoration it serves as the chapel of the Chamber of Deputies, so access follows the parliamentary complex rather than normal parish hours; check locally before going.

The brick bell tower dates to the 12th century, and in the apse survive remains of frescoes showing Christ between Saints Gregory of Nazianzus and John Chrysostom. During the 1977-1987 restoration, a room was uncovered and identified as the only surviving part of the original oratory.