Known as the “Great Church” or “Magna Ecclesia” in Latin, the first church was built at the same location where there had been a pagan temple before. It was Constantius II who inaugurated Hagia Sophia on 15 February 360. From the chronicles of Socrates of Constantinople, we know that the church was built by the orders of Constantine the Great.

This first church was a wooden-roofed basilica with a nave flanked by two or four aisles, each carrying a gallery storey. It was preceded by an atrium. This church was largely burned down in 404 during riots since patriarch John Chrysostom was sent into exile by the Emperor Arcadius.