It is the seat of the Bishop of Susa and is dedicated to Saint Justus of Novalesa (Italian: San Giusto).

In origin it was the church of the Benedictine Abbey of St. Justus, established in 1029 by Marchese Olderico Manfredi to house the newly discovered relics of Saint Justus.

The façade has terracotta decorations and is joined to a Roman gate of the 4th century, the Porta Savoia, to the south.

Halfway along the south side stands the campanile, with six levels of mullioned windows.

It contains a baptistry which is earlier than the present church, and a statue supposedly of Adelaide, Marchioness of Turin, daughter and heiress of Olderico Manfredi and wife of Otto, Count of Savoy, ancestress of the Royal House of Savoy.