The feast of San Grato (Saint Gratus), patron saint of Aosta and of the entire diocese of the Aosta Valley, is celebrated in Aosta on 7 September.

The most solemn moment of the festival is the procession that carries the relics of the saint through the streets of the center of Aosta, kept in the precious reliquary chest from the medieval era, a jewel of Gothic art begun by Guglielmo di Locana and completed by the Flemish goldsmith Jean de Malines.