The Church of San Gregorio is dedicated to St. Gregory the Illuminator, patron saint of Armenia. It is the oldest consecrated church in the city of Bari and is believed to date back to the 10th century. The church is situated within the fortified enclosure of the St. Nicholas Citadel complex, once the seat of the Byzantine Catapan. The Citadel used to include many Greek churches (St. Eustratius, St. Nicholas, St. John the Evangelist), as well as administrative buildings (the Praetorian Prefecture, the guard’s gatehouse, and so on). In 1089, the new Norman rulers demolished all the structures there within except for the Church of St. Gregory, and consigned the area to the city for the construction of the new basilica dedicated to St. Nicholas. The church was probably spared thanks to its amplitude and intrinsic value. The name of St. Gregory first appeared in a document dated 1015, found in the Archives of Saint Nicholas. It refers to the Armenian cleric Mele "cleric, abbas, custos et rector ecclesiae sancti Gregorii" (cleric, abbot, protector and rector of the Church of St. Gregory).
The people of Bari cherished the church, and the eleven epitaphs bearing the surnames of influential families of Bari found on the outer walls confirm this. An inscription dated 1308 on the building’s inner south façade states that, for a certain period of time, the church had been used as a burial ground for members of the St. Gregory Confraternity, hosted in the church as of 1497. In the mid-1900s, the church underwent "in-style restorations” that eliminated 17th and 18th century modifications. Nonetheless, the church has managed to perfectly preserve its Romanesque appearance, with its tripartite façade that corresponds to the three interior naves. The church of St. Gregory also houses the wooden and papier-mâché statues of the Paschal Mystery that are carried in the Good Friday procession on alternate years. In the local dialect, the people of Bari have nicknamed the statues “vendelùse”, i.e. "wind arousers”.