Gratus of Aosta was a fifth-century bishop who served the diocese of Aosta. Originally a priest, he participated in the Council of Milan in 451, where he acted on behalf of Bishop Eustasius to support the condemnation of the Eutyches heresy. His religious formation likely followed the monastic traditions established by Eusebius of Vercelli. He later presided over the movement of several holy relics within his city around the year 470. He is remembered as the patron saint of Aosta and is honored in the Catholic tradition.