The cathedral was built on the site where two temples dedicated to Apollo and Neptune stood in ancient times. Already in the 4th century stood the Basilica of Santa Restituta, then, in 570, a church dedicated to the Savior was built, also called Stefania, after the bishop Stephen, who wanted it. It was King Charles I of Anjou who wanted the new church built, which was erected by his son Charles II and inaugurated in 1315. Due to an earthquake in 1456, the church was destroyed but later rebuilt by King Alfonso I of Aragon.
Numerous renovations were made over the centuries. The facade, restored several times, was completely redone in 1887 by Enrico Alvino. The third chapel on the right is called the Treasure of San Gennaro where the ampullae containing the miraculous blood of the Patron of Naples are kept. On either side of the chancel is the Carafa Chapel, the work of Tommaso Malvito and the pride of Neapolitan Renaissance art. The Chapel of Santa Restituta, then, represents the oldest Neapolitan basilica: legend has it that it was built at the behest of Emperor Constantine. There is, finally, the very ancient 5th-century baptistery of San Giovanni in Fonte.